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RSC-FORTH User`s Manual

1. 3FCB 0 lt 3FCO 0 3FB5 VS 3F9B NOT 3F73 ELSE 3F63 THEN 3F1E IF 3EFC REPEAT 3EE6 AGAIN 3EAC UNTIL 3E99 BEGIN 3E79 BITCLR 3E29 RMB 3DF1 8MB 3DE1 BIT 3DC1 JSR 3DB1 STY 3DA1 LDY 3DB1 CPY 3D71 CPX 3D61 STX 3D41 ROL 3D31 LSR 3D21 INC 3D01 ASL 3CF1 STA 3CE1 SBC 3CC1 LDA 3DB1 EOR 3CA1 CMP 3C81 ADC 3C73 TXS 3C65 TYA 3C49 TSX 3C3B TAY 3C2D TAX 3C11 SED 3C03 SEC 3BF5 RTS 3BD9 PLP 3BCB PLA 3BBD PHP 3BA1 NOP 3B93 INY 3B85 INX 3B69 DEX 3B5B CLV 3B4D CLI 3B31 CLC 3B23 BRK 3A54 RP 3A34 TOP 3A27 3A1C Y 3A04 Y 39F8 X 39EC MEM 39D4 A 39A1 SETUP 3993 BINARY 3976 PUSHOA 3967 POPTWO 3958 POP 3940 PUSH 3933 NEXT 3926 XSAVE 390D W 3903 IP 38F8 N ST of RSC FORTH Assembler Words 352 7 1 1 CODE Definitions The CODE word defines a word written in assembly code called a CODE definition in a similar manner as the word defines a word written in FORTH a colon definition The assembler vocabulary is automatically selected as CONTEXT when CODE is encountered The name following CODE is entered into the dictionary as the FORTH word for the CODE definition Assembly language routines or program segments in CODE definition form are often referred to as CODE or code in general FORTH literature Assembly language instructions in RPN format see Section 7 2 are then entered along with any instruc
2. At compile time BEGIN leaves its return address and n for compiler error checking char INPUT OUTPUT blank A constant that leaves the ASC character value for blank i e 20 on top of stack addr n MEMORY blanks Fills an area of memory beginning at addr with the ASC value for blank the number of bytes specified by count n will be blanked addr MASS U b 1 k Leaves the address of a user variable containing the number of the mass storage block being interpreted as the input stream If the content is zero the input stream is taken from the terminal n addr MASS block Leaves the first address of the block buffer containing block n If the block is not already in memory it is transferred from mass storage to whichever buffer was least recently accessed If the block occupying that buffer has been marked as updated it is rewritten onto mass storage before block n is read into the buffer If correct mass storage read or write is not possible an error condition exists Only data within the latest block referenced by BLOCK is valid by byte address due to sharing of the block buffers n is an unsigned number Also see BUFFER R W UPDATE and FLUSH WORD BOUNDS BRANCH BUFFER C CON STACK
3. TABLE OF CONTENTS Section Title 12 3 Using Mass SbEOFage 6 4 ria UE Gh tw ee sec oig 12 3 1 Data Storage and Retrieval the Virtual RAM 12 3 2 Program Loading and Overlays 12 4 Sources Code HALEINGS lt oka a ii APPENDIX A RSC FORTH Functional Summary e APPENDIX B RSCCFORGBH GLOSS ALVY e A oe sos Neri v suddetto eer APPENDIX e RSC FORTH Assembler Functional Summary APPENDIX D RSC FORTH Assembler Glossary eee APPENDIX E Error Messages and Recovery o o ooooooooooo ooo Hel Standard Error Message em e e a E 2 Standard Error Message Word ES RSC FORTH Error DefintELORS vajar aaa Ex 24 Disk EROS ia A ARBRES APPENDIX F Page Zero Memo Ey Map lt a a ie hs ES da eae APPENDIX G USER Variables RAM Map ooooooooooooooooooooo APPENDIX H ASC Character Set dia io a il a ads APPENDIX PORTE Stig WOAS ii ia a das APPENDIX J USER 24 Hour Clock Program in FORTH APPENDIX K Utility Examples 4 42 dead he ed eee e dw ate eee APPENDIX L RSCSEORTH Versus EIG EORTH 4 4499 rabo whe eta oi APPENDIX M RSC FORTH Floppy Disk Interface APPENDIX N RSC FORTH Screen Numbers Versus Track N mbers uw Lexus Seg
4. Table E 1 RSC FORTH Error Message Number Message Definition Action 0 Echoed word was Define the named the last one inter item Check number preted Name is not conversion base in the dictionary and is not a number 1 STACK Parameter stack Don t pull more EMPTY is empty items off the Stack than are there 2 DICTIONARY The dictionary Increase space for FULL space is used dictionary by up FIRST HERE FORGETing entries is less than AO or moving FIRST 3 HAS The address mode Use a correct INCORRECT for that assembler address mode ADDRESS op code is See R6500 MODE incorrect Programming Manual 4 NOT The dictionary entry Be aware that the UNIQUE name just created new definition of is not unique name obscures the old one and all future refer ences to lt name gt will be to the new entry often an advantage Table E 1 RSC FORTH Error Message Continued Number Message Definition Action 5 Not assigned x 6 DISC The disk block This is available RANGE asked for is out for the user to of range put in his definition of R W 7 FULL The parameter Remove some stack STACK Stack is full item DROP or more than 50 output items 8 DISC There has been a This is available ERROR disk er
5. The general format is BEGIN lt assembly code gt lt cc gt UNTIL lt continuing assembly code gt For example enter the CODE definition for LOOP TEST HEX O VARIABLE TICK CODE LOOP TEST 6 LDA N STA BEGIN TICK DEC N DEC UNTIL NEXT JMP END CODE Note where the variable TICK and LOOP TEST are located in the FORTH dictionary by using VLIST VLIST 42A LOOP TEST 418 TICK 40B TASK 3844 ADMP 3805 DUMP 37CF FORMAT 367E FMTRK 3674 BANKEXECUTE 3664 BANKEEC 3657 BANKC OK SPACE bar pressed Also find the start of the next dictionary entry HERE RETURN 43C A disassembly of the code is as follows 042E A9 06 LDA 06 0430 85 51 STA 51 0432 CE 1C 04 DEC 041C Address of TICK 0435 C6 51 DEC 51 0437 DO F9 BNE 0432 0439 4C 28 F4 JMP F428 This shows you how the assembly code is generated for a typical conditional loop First the temporary storage byte at address N is loaded with the value 6 The beginning of the loop is marked at assembly time by BEGIN Memory at TICK is decremented then the loop counter in N is decremented Of course the CPU updates its status register as N is decremented Finally a test for Z 1 is made if
6. BEGIN THEN UNTIL AGAIN IF WHILE ELSE REPEAT Here again the assembler words end with a comma to indicate that code is being produced and to clearly differentiate from the high level form One major difference occurs High level flow is controlled by run time Boolean values on the data stack Assembly flow is controlled instead by processor status bits You must indicate which status bit to test with one or two FORTH condition code cc words just before a conditional branching word i e IF UNTIL or WHILE The conditional specifiers for the CPU are FORTH Condition Code cc Test Words Function Processor Status Bit CS carry set C 1 0 lt less than zero N 1 0 equal to zero 1 VS overflow set V 1 CS NOT carry clear C20 0 NOT positive N 0 O NOT not equal zero Z 0 VS NOT overflow clear V 0 BITCLR state of bit in zero page location N A BITSET state of bit in zero page location N A 7 6 1 Conditional Looping A conditional loop is formed at assembler level by placing the instructions to be repeated between BEGIN and UNTIL Precede UNTIL by a conditional specifier e g 0 lt The assembler generates the proper conditional branch machine instruction e g BEQ to test the processor status and to conditionally branch back to the machine instruction immediately after the BEGIN
7. If the Boolean is false nothing happens but if it is true one of three things happen depending on the value of the user variable WARNING If WARNING is zero the number n is printed as an error message If WARNING is greater than zero a disk is assumed to be in use Then n becomes the line number relative to line 0 screen 4 of drive 0 and the contents of that line number are displayed in ASCII The line number may be negative zero or positive and greater than fifteen The line number is simply an offset from line 0 screen 4 If WARNING is less than zero the word ABORT is executed Rp 1 I E 3 RSC FORTH The error conditions detected by RSC FORTH are listed in Table ERROR DEFINIT ONS increased utility the two most common errors are given in and warning message 4 error message 1 STACK EMPTY E 1 English NOT UNIQUE For These are The last action of error messages processing is to clear the stacks and execute QUIT However the warning message NOT UNIQUE is simply output it has no effect on the stacks and execution continues normally code word being defined the name of th and the message number or message interpreted Error message number 3 is slightly different in that it prints the name of the assembler op cod word being
8. PC PFAPTR SCCR SELECT UC L UR W G FORTH 1 0 gt LINE 2DUP ALLOT BANKEE SCDR SOURCI UFIRST XOFF GI BANKEXECUTE CLD WR C BOUNDS M CYLIND ER DP FINIS EJE ER NTVEC EMTOP p m M E P PICK SCSR U lt ULIMIT XON b The following words are in FIG FORTH 1 0 but are not in RSC FORTH V1 6 however some of the words are in the RSC FORTH Assembler vocabulary Word Name Where Used Comment ORIGIN system LOADING system BACK system BLOCK READ user disk word DREAD BLOCK WRITE user disk word DWRITE DLIST duplicate name VLIST DMINUS new name DNEGATE DRO disk DR1 disk FLD not used MINUS new name NEGATE MOVE N A word addressing computers NEXT RSC FORTH Assembler OUT not used POP RSC FORTH Assembler PUSH RSC FORTH Assembler PUT RSC FORTH Assembler R system TRAVERSE system TRIAD disk X System null APPENDIX M FLOPPY DISK INTERFACE The R65F11 R65F12 hardware interface is configured to directly interface with a 1793 type Floppy Disk Controller FDC device with minimal support circuitry required Figure M 1 shows the
9. D TO CLEAR SCREENS gt S WIPE BLANKS etc BLOCK 1024 BLANKS SCR 13 O WOR 1 2o Ae Sec 3 WIP 4 5 6 7 8 9 10 11 12 13 14 aou The words LIST before text is placed in it with LINE Th UPDATE FLUSH and gt LINE work together in words for manipulating character data are already supplied NE and LIST The following code that a screen should be listed e act of listing a screen makes that screen the current screen and operations are directed to it The word LIST also prints the screen number and the number placing text in that screen Given the line gt LINE fetches the current screen number then moving the following text string into it On buffer gt LINE uses LINE to output 16 lin es of 64 characters each LIST of each line for reference when number as a parameter the word places blanks in that line before ce the text is in the proper flags the buffer as having new data in it and that data will automatically The word WIPE blocks with spaces takes the screen number left overwrites anything written in the screen it 12 7 thus preparing the screen for editing Because WIPE be written to mass storage if the buffer is needed on the stack and fills all of its must be u
10. The loop index value is kept by the system and incremented automatically The FORTH word I retrieves this index and copies it onto the stack In the example above the index value is zero the first time through the loop then it is 1 2 etc through 24 In this example the index is printed each time SERIES takes no arguments from the stack and returns no results 4 21 The recommended code writing style for using DO and LOOP is to have the entire loop in a single line if possible if not LOOP should be indented to the same column as its corresponding DO This style makes the program s structure easier to see The definition NSERIES N VARIABLE SERIES CR 0 DO I LOOP creates NSERIES which is almost like SERIES except that it takes one argument from the stack the number of times around the loop Now execute NSERIES 10 NSERIES 01234506789 OK Redefine SERIES now in terms of NSERIES as SERIES PRINT A SERIES 20 NSERIES This redefinition will cause a NOT UNIQUE warning message to be printed The warning can be ignored in this case remember its purpose is to let you know that the word has also been defined previously As mentioned before FORTH allows any word to b
11. addr assembly time RETURN nl gt NZ run time put zero a At assembly time constant which leaves the machine address of the return point which at run time will write a zero as high byte and the accumulator as low byte over th existing data stack 16 bit value nl addrB 1 addrW 3 CONTROL assembly time run time repeat Occurs in a code definition in the form BEGIN ese OG WELDE REPEAT WORD REPEAT Cont RP uN E Q SETUP THEN STACK NOTATION DEFINITION GROUP At assembly time REPEAT assembles as JMP instruction to the instruction immediately following the BEGIN word At run time REPEAT unconditionally branches back to its matching BEGIN 101 assembly time STACK return pointer Used in a CODE definition in the form RP LDA or RP 3 STA Addresses the top byte of the return stack containing the low byte by selecting the X mode and leaving n 0001 n may be modified to another byte offset Before operating on the return stack the X register must be saved in XSAVE and TSX executed Before returning to NEXT the X register must be restored 2 second Used in a CODE definition in the form assembly time STACK SEC LDA or SEC 1 S
12. 3 When the Counter B underflow occurs the contents of the Latch C is loaded into the Counter B and the CB output toggles to a high level and stays high until another underflow occurs Latch B is then down loaded and the CB output toggles to a low level repeating the whole process Latch Value Count Value Figure 9 8 Counter B Retriggerable Interval Timer Mode Lh o 143 Counter B Lstch B 0 2 amp 4 Counter 8 lt Lstch C P Figure 9 9 Counter B Pulse Generation 9 18 SECTION 10 NOTES ON STYLE AND PROGRAM DEVELOPMENT T 10 1 GENERAL Like most other programming languages FORTH is not particularly readable to someone who is not familiar with it Because FORTH is unique among programming languages even experienced programmers have difficulty at first FORTH is unlike their past experience After reading this manual FORTH should be understandable and some practice in coding will sharpen the eye The key to easily readable FORTH code lies in logical factoring of key words and in choosing appropriate names for words Correct FORTH code should read in an almost natural English way for the higher level key words if these practices are followed Factoring means writing a word as a collection of lower level words that actually name the functions performed by this word
13. The word HERE returns the address of the next available dictionary location HERE can be used to determine the size i e the memory required of a colon definition The procedure is to type HERE puts current dictionary address on stack Enter the colon definition lt name gt Enter the current dictionary address on stack swap to subtract the smaller address from the larger and then print the size of the defined word HERE SWAP Enter the following example of a square function Note the first available dictionary location before and after entry of the SQUARE colon definition The length of the colon definition in the dictionary is 15 HEX OK HERE DUP RETURN 411 OK SQUARE DUP OK HERE DUP RETURN 426 OK SWAP RETURN 15 OK Check the operation of the SQUARE word DECIMAL 4 SQUARE RETURN 16 4 9 2 Use PAD for Temporary Storage A common location for temporary storage in most FORTH systems is the address returned by the word PAD and the memory above In RSC FORTH PAD returns a starting address two bytes below the Terminal Input Buffer TIB in the USER area of RAM PAD must be used with caution therefore in RSC FORTH the space below PAD is used by RSC FORTH itself for temporary storage Let s restart and check the starting addr
14. TABLE OF CONTENTS Section Title Page 7 RSC FORTH ASSEMBLER Tol The Assembly Process svete aid See X e ated ee Pee hoe Gee ROE dod Toll CODE Definitions c2l65x we ET RE es LS 7 1 2 Assembly Time Versus Run Time 7 3 Fales CODE Definiticn Example mr para are ee oe 7 3 Lazo ASSembler Op eoQesS TedMe ese DS Uie vue 7 4 1 2 1 Single Mode Op COdes semia eet a nated a ans 125 T M ltaz cMode dOp GQOdesS del ad da oe 7 6 Taa Addressing Modes Eli oe Sc acd Wea ee MIS RU 7 5 74 ROSO02 ConventronsS iX b4 3 vA Pade davai cee wes 7 6 7 4 1 Stack Addressing srr sewn wee AE ES 7 6 Tela Return Stacki sa ERA tigre wy atcha ei ES wore m ETE o FORTH Registers eds DR EUR EU se RU UR on e ere 7 8 Tol Assembly REGUSECES Ql veux 9 ea AM ye xe a a 7 8 4 542 CPU REGLSECTS Siesta ee aa oe ae ead ae ee A 9 LS RAM sl rt Ld A de A te Sit dr dde 7 9 JU Dud N A bea COSI Xd exque exce Wen ME RU S P ew 7 9 dubub SU AA A AA 2 ered hoe ido 7 10 de CONE roi BLOW cg a ARO Th REN Sr Ene periere 7 10 dou Conditional LOOPING 4 we soe qwe s 7 11 142632 Conditional Executaon fice wd tei MER eke e 7 12 7 6459 Conditional Nesting disc ria S e RS 7 13 7 6 4 Some Nesting Examples ee ee 7 14 Pel RECUBM Of CONETOL ida asd des seat eels ete Gua Sete E nea RS ae 7 17 T8 Assembler Security a
15. addr SECURITY U fence Leaves the address of a user variable containing an address below which FORGETting is trapped To forget below this point the user must alter the contents of FENCE addr n b MEMORY MEITAT Fills n bytes beginning at addr with the byte pattern b MONITOR EX s Marks the end of the input data stream into the compiler B 29 WORD FIRST FLUSH FORGET FORMAT FORTH FMIRK STACK NOTATION DEFINITION GROUP ATTR n MASS WEES EY Leaves the first lowest address of the data or mass storage buffer MASS flush Writes all blocks to mass storage that have been flagged as UPDATEd An error condition results if writing to mass storage is not completed DICTIONARY forget Executes in the form FORGET lt name gt Delete from the dictionary lt name gt which is in the CURRENT vocabulary and all words added to the dictionary after lt name gt regardless of their vocabulary An error message will occur if the CURRENT and CONTEXT vocabularies are not currently the same Failure to find lt name gt in CURRENT or FORTH is an error condition ni n2 MASS format Format nl tracks on disk number n2 VOCABULARY forth The name of the primary vocabulary Execution makes FORTH the CONTEXT vocabulary New definitions become
16. 456 RETURN O 456 23145 RETURN O 23145 879 RETURN 1 879 1289 4 RETURN 1 12894 Change to hexadecimal and repeat the examples Notice the difference since each hexadecimal digit represents four binary bits HEX 456 RETURN O 456 23145 RETURN 2 3145 879 RETURN 1 879 1289 4 RETURN 2 2894 5 2 2 Printing Double Precision Numbers Now that you understand how double precision numbers are stored on the stack let s look at two FORTH words that print the data in double precision format The word D pronounced d dot prints the top two numbers on the stack as a 32 bit number left justified Repeat the previous examples in decimal DECIMAL 456 CR D 456 23145 CR D 23145 879 CR D 879 1289 4 CR D 12894 It is often desirable to print the data right justified The word D R d dot r prints a double precision number right justified in a variable width field The top number on the stack is the column in which the least significant digit of the data is to be printed while the second number is the double precision number the data to be printed Try the example data one more time but right justify it in the 30 column field as follows if the number prints in the wrong column you forgot to switch back to decimal 456 30 CR D R 456 23145 30 CR DiR 23145 879 30 CR D R 879 12
17. Converts the line number n1 and the screen number n2 to the disk buffer address containing the data A count of 64 indicates the full line text length See LINE PRIMITIVE The run time procedure compiled by LOOP which increments the loop index and tests for loop completion See LOOP dl addr1 d2 addr2 PRIMITIVE Converts the ASC text beginning at addrl 1 with regard to BASE The new value is accumulated into dl being left as d2 addr2 is the address of the first unconvertable digit See NUMBER nl n2 n3 ARITHMETIC times Multiples nl by n2 and leaves the product n3 nl n2 n3 n4 ARITHMETIC times divide Multiplies nl by n2 divides the result by n3 and leaves the quotient n4 n4 is rounded toward zero The product of nl times n2 is maintained as an intermediate 32 bit value for a greater precision than the otherwis quivalent sequenc nl n2 n3 WORD MOD I BUF LOOP STACK NOTATION DEFINITION GROUP ATTR nl n2 n3 n4 n5 ARITHMETIC times divide mod Multiplies nl by n2 divides the result by n3 and leaves the remainder n4 and quotient n5 A 32 bit intermediate product is used as for The remainder has the same sign as nl nl n2 n3 ARITHMETIC plus Adds nl to n2 and leaves the arithmetic s
18. LITERAL STACK NOTATION DEFINITION GROUP ATTR pfa Tf a DICTIONARY f a Converts the parameter field address pfa of a dictionary definition to its link field address lfa SSS MASS Leaves the highest address plus one available in the data or mass storage buffer Usually this is the highest system memory nee MASS list Lists screen n to the current output device CORE d PRIMITIVE aq Within a colon definition LIT is automatically compiled before each 16 bit literal number encountered in input text Later execution of LIT causes the contents of the next dictionary address to be pushed to the stack n compiling COMPILER literal If compiling then compile the stack value n as a 16 bit literal which when later executed will leave n on the stack This definition is immediate So that it will execute during a colon definition The intended use is XXX calculate LITERAL Compilation is suspended for the compile time calculation of a value Compilation is then resumed and LITERAL compiles this value into the definition WORD LOAD LOOP M M M MOD STACK NOTATION DEFINITION GROUP ATTR n MASS load Begins interpretation of screen n by making it the input stream preserves th
19. To move the program to the second RAM at power on enter FORGET TASK HEX 400 ALLOT TASK The lower addressed RAM can remain in the target system if needed By allotting blocks in multiples of 0400 any 1K byte boundary can be used for the autostart vector Another independent question to be addressed is that of normal or target compiled code No action is required if normal code is desired In order to initiate target compilation action must be taken at power on The sequence FORGET TASK HEX 600 H C TASK causes codes to be generated at address 0404 and up and dictionary heads to be placed at 0600 and up Depending on the system configuration and RAM available the codes might need to be at other addresses A combination of the two methods above might be required For example FORGET TASK HEX 400 ALLOT 1800 H C TASK puts tie codes at address 0800 and the heads at 1800 After a program has been entered tested and debugged and re entered in the correct memory location and compiled format it is ready to have the autostart pattern added This is the very last step before transferring the image to PROM This should be done with great caution Once a program is set for program autostart the development ROM cannot be reentered by RESET 13 2 Addition of the autostart pattern is extremely easy The word AUTOSTART generates the autostart pattern and loads the vector
20. 4 13 1 Input a Character from the Terminal with KEY The word KEY accepts a single character from the keyboard returning its ASC value to the top of the stack It is the opposite of EMIT see Section 4 12 3 It is often used to accept a single letter menu choice from the user The entry procedure is KEY lt RETURN gt lt character gt Note that the entered character is not displayed Upper or lower case letters may be entered however FORTH words must be in upper case Clear the stack with an undefined word enter a character and check the entered value on the stack TOD y EX KEY RETURN A Type A Notice the hexadecimal representation of the ASC code for the entered number Change the 1 0 base to DECIMAL and check the value again DECIMAL S 65 Use EMIT now to output the numbers to the display EMIT lt RETURN gt A You can use the words KEY and along with the 1 0 base to easily convert the ASC code for an entered character into the number base of your choice This is especially useful if you do not have an ASCII HEX DECIMAL conversion table handy To enter a number and display it in hexadecimal use KEY lt RETURN gt lt input character gt HEX To display an entered number in decimal use KE
21. WORD VOCABULARY Cont VLIST WARNI WHILE NG STACK NOTATION DEFINITION GROUP ATTR New vocabularies chain to FORTH This is when all of dictionary search through a vocabulary is exhausted FORTH will be searched VOCABULARY v list Lists the names of the definitions in the CONTEXT vocabulary Depression of any key will terminate the listing addr SECURITY U warning Leaves the address of user variable containing a value controlling messages If value 1 mass storage is present and screen 4 of drive 0 is the base location for messages If value 0 no disk is present and messages will be presented by number If valu 1 execut ABORT for a user specified procedure See MESSAGE and ERROR flag run time CONTROL ERG addrl nl gt addr1 nl addr2 n2 while Occurs in a colon definition in the form BEGIN WHILE tp REPEAT At run time WHILE selects conditional execution based on Boolean flag If flag is true non zero WHILE continues execution of the true part through to REPEAT which then branches back to BEGIN If flag is false zero execution skips to just after REPEAT exiting the structure At compile time WHILE emplaces OBRAN
22. nce DICTIONARY comma Stores n into the next available dictionary memory cell advancing the dictionary pointer a gt DICTIONARY comma slash Stores n into the next available heads dictionary memory cell advancing the dictionary pointer DP ni n2 ns ARITHME minus Substracts n2 from nl and leaves the difference n3 e I rj MASS next screen Continues interpretation with the next virtual storage screen ul u2 ARITHMETIC b c d Converts a number to its binary coded decimal BCD equivalent nl nl if zero STACK nl nl nl non zero minus dup Reproduces n1 only if it is non zero This is usually used to copy a value just before IF to eliminate the need for an ELSE clause to drop it WORD TRA NG STACK NOTATION DEFINITION GROUP ATTR pfa Wd 6E found DICTIONARY Tt not found dash find Accepts the next text word delimited by blanks in the input stream to HERE and searches the CONTEXT and then CURRENT vocabularies for a matching entry If found the dictionary entry s parameter field address its length byte and a Boolean true is left Otherwise only a Boolean false is left addr nl addr n2 FORMAT dash trailing Adjusts the character count nl of a text string beg
23. 5 6 2 CONTEXT and CURRENT Specify Vocabularies At any given time two vocabularies are in effect CONTEXT and CURRENT CONTEXT specifies the vocabulary in which dictionary searches begin while CURRENT gives the vocabulary into which new definitions are placed Often CONTEXT and CURRENT are the same g when RSC FORTH is initialized initial entry or COLD word both of them point to the FORTH vocabulary But when a CODE definition is being assembled the CONTEXT vocabulary is ASSEMBLER while CURRENT is usually FORTH or something else CURRENT would be ASSEMBLER only if you were adding new capabilities e g macros to the assembler To set the CONTEXT just execute the name of a vocabulary e g ASSEMBLER switches to the ASSEMBLER vocabulary To set the CURRENT the word DEFINITIONS changes the CURRENT to the CONTEXT So to change both of them to ASSEMBLER execute ASSEMBLER DEFINITIONS Now any new colon CODE or other definition will go into the ASSEMBLER vocabulary Remember to get back by executing FORTH DEFINITIONS after you are done extending the assembler Incidentally any colon or other new definition will set CONTEXT back to CURRENT This is done to help the programmer avoid errors So if you are in FORTH and then execute just ASSEMBLER without DEFINITIONS and then define any new words they will go into FORTH and also the CONTEXT will be set back to FORTH i e executing ASSEMBLER alone will have
24. FORTH Conventional Assembler A ROL ROL A A distinguishes A 1 LDY LDY 41 from hex number OA DATA X STA STA DATA X DATA Y CMP CMP DATA Y 60 X ADC ADC 60 X POINT Y STA STA POINT Y VECTOR JMP JMP VECTOR The words DATA POINT and VECTOR specify machine addresses defined by prior VARIABLE or CONSTANT words In the case of 60 X ADC the operand memory address 0060 was given directly This is occasionally done if the usage of a value does not justify devoting the dictionary space to a symbolic value 7 4 R6502 CONVENTIONS 7 4 1 Stack Addressing The parameter stack is located in z page and is usually addressed by z PAGE X This stack starts at 00C2 and grows physically downward The X index register is the data stack pointer Thus incrementing X by two removes one data Stack value decrementing X twice makes room for one new data stack value 16 bit values are placed on the stack according to the R6500 convention the low byte is at low memory with the high byte following This allows indexed indirect X instructions to b xecuted directly off of a stack value The top and second stack values are referenced often enough that the support words TOP and SEC are included Using TOP LDA assembles LDA 0 X and SEC ADC assembles ADC 2 X TOP leaves 0 on the stack and sets the address mode to X SE
25. a 1000 To be efficient when doing more than one gas mileage check the current odometer reading should be saved as m0 for the next calculation 10 2 b C Scaling To correctly scale the calculation for integer computation you must first decide the level of precision desired in the answer If you want mpg to a tenth of a mile per gallon distance in miles price to a tenth of a cent and amounts in cents then m1 m0 p 10 mpg 10 a If we enter p without the decimal we get p times 10 automatically and the result will come out in 10 s of mile per gallon as desired Program Design Coding and Checkout If the data are recorded in a data book as miles price and amount it is convenient to enter them as written therefore the stack would look like this ml pa and they would all be 16 bit numbers Given the data on the stack as described above and the odometer correction and price adjustment necessary the principle word looks without any comments like this MPT ROT TRUE MILES ROT CENTS GAL ROT MPG where the ROT words bring the stack values up to be operated on by the fairly obvious correction and adjustment words The computes the final operation mp a and the word MPG prints the answer out in a nice format with a decimal point where we expect it Now that we have the top level structure let us define the lower level words
26. Now find the end of the dictionary HERE RETURN 411 OK Remember HERE is defined as DP so DP RETURN 411 OK has the same effect Before beginning target compilation verify the operation of DP and HERE to be the same as DP and HERE DP RETURN 411 OK HERE RETURN 411 OK If you begin target compilation now TASK will be left in the codes dictionary Temporarily drop TASK from the dictionary FORGET TASK Begin target compilation by specifying a heads dictionary address HEX 600 H C Now add TASK back to the dictionary with a colon definition and run a short VLIST 607 TASK 3844 ADMP 3805 DUMP 37CF FORMAT 367E FMTRK RETURN OK Note that the VLIST shows the PFAPTR of TASK to be at 607 Displaying the CFA of TASK shows where the actual code is in memory TASK CFA RETURN 404 OK HEADERLESS You can verify that is indeed a true value now and test the functions of the dictionary control words mentioned above HEADERLESS lt RETURN gt 1 OK DP RETURN 408 OK DP RETURN 609 OK HERE lt RETURN gt 408 OK HERE lt RETURN gt 609 OK Examining memory at 400 and 600 with the DUMP breakdown of the two memory spaces is as follows 404 405 406 407 408 ADDRESS OF COLON INTER PRETER 600 601 602 603 604 605 606 60
27. current BASE that failing an error condition exists DEFINING LE semi colon Terminates a colon definition and stops further compilation If compiling from mass storage and the input stream is exhausted before encountering an error condition exists WORD COD Ei DUMP STACK NOTATION DEFINITION GROUP ATTR DEFINING semi colon code Used in the form GI lt nam END COD o stirs te CODE lt assembly code gt E D Stops compilation and terminates a new defining word name by compiling CODE Sets the CONTEXT vocabulary to ASSEMBLER assembling to machine code the following mnemonics When name is later executed in the form name lt namex gt to define the new namex the code field address of namex will contain the address of the code sequence following the CODE in name Execution of any lt namex gt will cause this machine code Sequence to be executed addr n I O semicolon dump Dumps n bytes starting at addr in ASC format in one semicolon record COMPILER semi colon S Stops interpretation of a screen S is also the run time word compiled at the end of a colon definition which returns execution to the calling procedure n2 flag COMPARISON less than Leaves a true fl
28. It is sometimes desirable to delete data from the stack without performing a COLD restart The stack may be cleared by trying to execute a word that is not currently defined in the FORTH dictionary This causes an error condition in which FORTH echoes the missing word followed by a see Appendix E for error descriptions and then clears the stack Initially the word Q is not defined in the FORTH dictionary and can be conveniently used to clear the stack Note also that entering a word that is not in the dictionary will also delete data that you may want on the stack so be careful with your word entries or you may have to re enter data or repeat prior steps Enter some numbers on the stack and display the stack contents 678 356 S 356 678 OK Type Q now and verify that the stack is cleared Q Q S EMPTY OK 4 1 4 Add and Subtract Let s now perform some simple arithmetic Put two numbers on the stack say 12809 135 lt RETURN gt Now type the add command lt RETURN gt The takes whatever two numbers are on top of the stack and adds them It removes those numbers by convention most FORTH operations destroy their arguments on the stack and replaces them with their sum Type lt RETURN gt to verify this The sum will be displayed as 12944 OK As before multiple operations can be placed on one line e g 12809 135 RETURN 12944 OK Subtract works in a sim
29. Moore C H FORTH a New Way to Program a Minicomputer Astronomy and Astrophysics Supplement 1974 number 15 pages 497 511 Phillips J B Threaded Code for Laboratory Computers Software Practice and Experience Vol 8 1978 pages 257 263 Rather E D and C H Moore The FORTH Approach to Operating Systems ACM 1976 Proceedings Association for Computing Machinery 1976 Rather E D and C H Moore and J M Hollis Basic Principles of FORTH Language as Applied to a PDP 11 Computer Computer Division Internal Report No 17 National Radio Astronomy Observatory Charlottesville VA Kitt Peak National Observatory Tucson AZ March 1974
30. Section 8 Handling Interrupts in FORTH explains how to use machine level and interpretive interrupts in FORTH Section 9 Programming the R65F11 1 0 explains how to use FORTH to program the R65F11 input output section These techniques can be used directly with the R6511 and can easily be applied to other peripheral devices Section 10 Notes on Style and Program Development discusses the general approach to programming in FORTH and provides an example program Section 11 Preparing an Application Program for PROM Installation tells how to structure and locate a FORTH application program in a PROM which will operate in conjunction with the R65F11 and R65F12 FORTH based microcomputers Section 12 Interfacing to Mass Storage tells how to prepare programs to Store and retrieve program and data from mass storage Blocks screens and buffers are described The technique to handle program overlays is also explained Appendix A RSC FORTH Functional Summary summarizes FORTH word operation by general area of usage Appendix B RSC FORTH Glossary defines each FORTH word in ASC sort order Appendix C RSC FORTH Assembler Functional Summary summarizes FORTH assembler word operation by area of usage Appendix D RSC FORTH Assembler Glossary defines each FORTH Assembler word in ASC sort order Appendix E Error Messages and Recovery
31. addr DIGIT 0 9 0 1 ossa 2 gt 3 9 3 4 osa gs S ARITHMETIC AND LOGICAL nl n2 sum D dl d2 sum nl n2 diff nl n2 prod nl n2 quot MOD nl n2 rem MOD nl n2 rem quot MOD nl n2 n3 rem quot Car nn quot U ul cu2 ud U nd ul 42 us M nl n2 d M di 11 252 102413 M MOD udl u2 u3 ud4 MAX nl n2 max item to Return Stack item from Return Stack Copy top of Return Stack onto stack Copy the nth item to top Return address of stack top position Return address of the return stack pointer Display stack contents without modifying the stack Initialize Parameter Stack Move top Retrieve Set decimal base Set hexadecimal base System variable containing number base Convert ASC to binary The number zero The number one The number two The number three The number four IL Add two 16 bit numbers Add two 32 bit numbers Subtract nl n2 Multiply Divide n1 n2 Modulo i e remainder from division Divide giving remainder and quotient Multiply then divide nl n2 n3 with double Like MOD but give quotient only Unsigned multiply leaves double product Unsigned remainder and quotient from double dividend Signed multiplication leaving double product Signed remainder and quotient from
32. external event on the CNTR line a Interval Timer Mode Interval Timer Pulse Generation and Pulse Width Measurement Modes are 02 The Event Counter Mode counts the occurrences of an The Counter is set to the Interval Timer Mode 00 when a RES signal is generated When the Counter is decremented from 0000 is the Latch value not FFFF In the Interval Timer mode the Counter is initialized to the Latch value by either of two conditions the next Counter value 2 When a write operation is performed to the Load Upper Latch and Transfer Latch to Counter address 001A the Counter is loaded with the Latch value Note that the contents of the Accumulator are loaded into the Upper Latch before the Latch value is transferred to the Counter The Counter value decrements by one count at the 62 clock rate The 16 bit Counter can hold from 1 to 65535 counts Timer capacity is therefore ps to 65 535 ms at the The Counter 1 MHz 02 clock rate or 0 5 us to 32 767 ms at the 2 MHz 02 clock rate Time intervals greater than the maximum Counter value can be easily measured by counting IRQ interrupt requests i application program IRQ interrupt routine n the When Counter A decrements from 0000 the Counter A Underflow IFR4 is set to logic 1 If the Counter A Interrupt Enable Bit IER4 is also set an IRQ interrupt request will be generated The Counter A Underflow bit in the Interrupt Flag
33. B 36 WORD MAX MCR MEMTOP MESSAG T MOD MODE MON STACK NOTATION DEFINITION GROUP ATTR nl n2 max ARITHMETIC max Leaves the greater of two numbers addr MISC mode control register System address constant for addr of Mode Control Register addr MASS memory top Initializes ULIMIT to addr and UFIRST to addr COC Clears disk buffers ig EE SECURITY message Displays on the selected active device the text of line n relative to screen 4 of drive 0 n may be positive or negative MESSAGE may be used to print incidental text such as report headers If WARNING is zero the message will simply be displayed as a number no mass storage nl n2 n3 ARITHMETIC min Leaves the smaller number n3 of two numbers nl and n2 nl n2 n3 ARITHMETIC mod Leaves the remainder n3 of nl divided by n2 with the same sign as nl addr PARAMETER U mode A variable used by the assembler MONITOR mon Exits to the micro Monitor leaving a re entry to FORTH WORD NEGATE NFA NMIVEC NOT NUMBER OFFSET OR STACK NOTATION DEFINITION GROUP ATTR AOS aS Sh ARITHMETIC negate Leaves the two s complement of a number i e
34. Load editing screen into buffer and compile or execute Automatically saves prior buffer contents if necessary BLOCK block addr Load editing screen into buffer and compile or execute Automatically stores prior contents of buffer if necessary A 8 A 14 MASS STORAGE B BUF B SCR BLK SCR tz LUSH MPTY BUFF BUF UFFER IST UJ Ed E 1 SELECT DREAD DWRITE FORMAT FMIRK gt LINE IR Continued n n addr addr P rae Se addrl addr2 f n addr fes pem addr blk f addr addr n n addr Been addr addr addr addr n b Hee Bic addr n err addr n err spe hel GA nl n2 n text System constant giving mass storage block size in bytes Number of blocks editing screen System variable containing current block number System variable containing current Screen number Mark last buffer accessed as updated Write all updated buffers to disk Erase all buffers Increment buffer address Fetch next memory buffer List a screen to the current output device Interpret next screen User read write linkage Variable containing address
35. R W is the primary word that interfaces FORTH to mass storage All of the FORTH logic which automatically handles the locating reading and writing of mass storage data ultimately winds up using R W However before R W can work properly it must have a set of data buffers to use As explained earlier RSC FORTH needs at least two buffers in order for the buffer rotation logic to work correctly The general steps in the process of setting up the block and data buffers is a simple procedure as summarized below the details are given in the following section Set the top high RAM of the data buffer area into ULIMIT Compute and set the start of the data buffer area into UFIRST Set USE and PREV to FIRST Clear the data buffer Initialize the block offset value OB NR In many cases steps 1 and 2 can be omitted The default value of the top of RAM for ULIMIT is a good choice unless special circumstances dictate that another value should be used MEMTOP may be used instead MEMTOP sets LIMIT and FIRST see below In steps 3 and 4 it is convenient to use FORTH to compute the actual values to store and to setup and clear the buffers to use The FORTH word EMPTY BUFFERS performs both these functions Steps 1 2 3 and 4 can be replaced if a standard two buffer memory area is desired Entering XXX MEMTOP where XXX is
36. WORD STACK NOTATION DEFINITION GROUP ATTR addr COMPILER U state Leaves the address of user variable containing the compilation state A non zero value indicates compilation STATI GI SWAP nl n2 n2 nl STACK W Swap W Exchanges the top two values on the stack TASK XS DICTIONARY task A no operation word which can mark the boundary between applications By forgetting TASK and recompiling an application can be discarded in its entirety Its definition is TASK THEN CONTROL then Used within a colon definition in the form TES a uo ENSE q CHEN OL TF ese lt p soo LAREN THEN is the point where execution resumes after ELSE or IF when no ELSE is present TIB addr INPUT OUTPUT t i p Leaves the address of user variable containing the starting address of the terminal input buffer addr b MEMORY toggle Complements the contents of addr by the 8 bit pattern byte TOGGLI GI TRAVERSE addr n addr DICTIONARY traverse Adjust the addr in a negative or positive direction depending on the sign of n until the contents of addr is greater than 7F n must be either 1 or 1 WORD TYPE U U U lt UABORT UC L UFIRST STACK NOTATION DEFINITION GROUP ATTR addr n INP
37. 24BE MODE 248B 245A 2419 CONTEXT USE DP 23E6 OFFSET IST of RSC FORTH Words 37CF 3657 35FD 35C3 3590 3560 3528 FORMAT BANKC MEMTOP MCR PE PB NTVEC 349F 3397 337D 335F 331A MON D R i ELSE 32BF END 3264 3165 3086 3056 3023 2FC9 DO FORGET H C DWRITE R W 2EFB BLOCK 2D41 2D00 2CC2 2COB VOCABULARY 2AE5 DLITERAL 29C8 28F1 MBER 2882 2840 ANKS 27F4 27AF 2765 2715 26B3 2604 25DB 25C0 2587 R ATLING 253E 250E 24DE 24B2 247C 244F 240F 23D8 UFIRST HLD BASE RO 4 0 E CONSTANT T4 SWAP DNEGATE E 0 lt R gt RPG XOR U XOFF KEY DIGIT LOOP CLIT DROP e BOUNDS 2 N EGATE 4 3 CYLINDE Figure 4 1 VLIST of RSC FORTH Words Cont d D UC BL 1 VARIABLE El TO SKNO CLD WRM L GGLE DUP OVI ER R
38. BLE The RSC FORTH structured assembler allows the creation of machine language procedures colon defin addressing functions i entered into a vocabulary in a similar manner as a FORTH colon definition I ed in the same manner by referring to the word name Ly language be structured and written similar to high level A function can first be rapidly written and debugged in and then recoded in assembly language for also execut recommended that assemb FORTH termi clarity of FORTH faster exec that may be more tim itions A separate ASSEMBLER modes conditionals and ot n R6500 assembly language nology expression tested for proper operation ution with a minimum of restructuring 7 1 THE ASS EMBLY PROCESS or code fficient than if defined in high level FORTH vocabulary provides th her support words necessary to program A function written in assembly language is op codes It is It is as it is often referred to in FORTH for The RSC FORTH assembler vocabulary is selected by the word ASSEMBLER or by the word CODE explained in the following paragraphs A separate ASSEMBLER vocabulary is linked ahead of the FORTH vocabulary The words in t
39. BUILDS DOES and CODE Each defining word is equivalent to a data type or class of operations Later we will learn how the user can creat ntirely new data types new defining words by using the special operations BUILDS DOES or CODE 4 10 4 USER USER is a defining word which creates a different kind of variable A user variable like an ordinary variable returns an address of where a value is stored But user variables store their values in a special user area which is normally in RAM from address 300 through 37F not in the dictionary which may be in ROM The name user area originated on large multi user FORTH systems Each user has a unique memory area for system variables e g the number base currently in effect for that user and the programmer s own variables The user variables are defined in Appendix G USER like CONSTANT and VARIABLE takes one argument from the stack but the argument is not an initial value instead it is an offset from 300 into the user area For example 60 HEX USER A 62 HEX USER B creates two variables A and B with offsets of 60 and 62 bytes respectively from the user variables base address at 300 USER is configured to allow offsets of 0 255 SEE Offsets between 54 and 60 should be used however to place the USER variables at 354 through 360 Note that offset val
40. NUMERIC decimal Sets the numeric conversion BASE to decimal base 10 for input output DEFINITIONS DI DL DN ISK SKNO TERAL EGATE STACK NOTATION DEFINITION GROUP ATTR VOCABULARY definitions Used in the form cccc DEFINITIONS Sets CURRENT to the CONTEXT vocabulary so that subsequent definitions will be created in the vocabulary previously selected at CONTEXT NUMERIC char nl n2 tf Valid conversion char nl ff Invalid conversion digit Converts the ASC character using base nl to its binary equivalent n2 accompanied by a true flag 1 If the conversion is invalid leaves only a false flag 0 addr muB MASS disk Single point entry to kernel disk handlers Perform disk operation read if f 1 write if f 0 write disk block n and memory location addr addr MASS U User variable containing the currently selected disk drive number 0 through 3 d d executing COMPILER o M compiling d literal If compiling compiles a stack double number into a literal Later execution of the definition containing the literal will push it to the stack If executing the number will remain on the stack al d 1 ARTTHMETIC d negate Leaves the two s complem
41. 3C CMP CS IF gt O LDA CS IF O LDA TICKS STA DAY INC O IF DAY 14 THEN THEN HEN EN N r gt r r 60 TICKS 1 STA TICKS INC TICKS LDA 18 CMP 24 INC EAR TIMER IRQ RN Figure J 1 24 Hour Clock Program Using a Machine Level J 3 Interrupt Handler 00 FO N FU U pH 40 RTH INI 0M ERI ERI 0 I SET IRQ VI R TA E E INITIALIZE THE TIMER CR C SET TB FR P ODL TBL C LOA D R RUN MODI TB VALUI 1 100 S E E E ODH TBH C ENABLE TIMER B INT ER C SEG TICKS CQ DD SAV TICKS 24 BEGIN TICKS 24 OVER PRINT n WAIT CQ NOT n 3 ENTER HRS amp PRINT SI t C8 DUP UNTIL DROE S R HOLD 4 TYP E TIM el 2 TICKS 14 t CQ R DD ING D r T O CHAR MESSAGE 601 DUP 30 EXP ECT 600 E BEGIN 1 UNTIL 601 600 C DUP CQ NULI OF FO Li R TYPE 0 FOUND CHARACTI M PRINT 60 O COUNT 30 D ECIMAL M E ESSAGE MIN TYPI TH CS ET TIME 100 U G ET SE 100 MOD TICKS C PIC
42. The outer text interpreter which sequentially executes or compiles text from the input stream terminal or mass storage depending on STATE If the word name cannot be found after a search of CONTEXT and then CURRENT it is converted to a number according to the current BASE That also failing an error message echoing the name with a will be given Text input will be taken according to the convention for WORD If a decimal point is found as part of a number a double number value will be left The decimal point has no other purpose than to force this action See NUMBER addr MI I R Q vector System address constant for addr of Low Level SC IRQ vector INPUT OUTPUT char key Leaves the ASC value of the next available character from the active input device addr kilo hertz A user variable that specifies the speed of the processor clock Currently unused and uninitialized PARAMETER addr D latest Leaves the name field address of the top most word in the CURRENT vocabulary CT ONARY CONTROL leave Forces termination of a DO LOOP at the next opportunity by setting the loop limit equal to the current value of the index The index itself remains unchanged and execution proceeds normally until LOOP or LOOP is encountered WORD LFA
43. upper address lines To accomplish this Port B must be used as The bank switching words allow a byte to be fetched from a particular bank stored in a particular bank and programmed into PROM in a particular bank A word in another bank can be executed also Unlike most other bank switching schemes these bank switching words alter the bank port during operation but return to the original processor time the programming of ban simplified calling bank upon completion Although this takes more The bank switching words k functions in high level is greatly BANKC BANKC BANKE EC and BANKEXECUTE are all in the kernel and can be used in standalone app each of these words is identical additional parameter tops the stack That is the nu the action on For instance 1234 6 BANKC fetches the contents of location 1234 Stack The entry 22 1234 6 BANKC to its non banking places a byte value of 22 at memory location 1234 i large programs that make it difficult to hav lications The function of namesake except one mber of the bank to perform in bank 6 and returns its value to the n bank 6 When working with the Development ROM the target program in RAM and a PROM in the memory map at one time BANKEEC may be invaluable After the program is complete it can be programmed into PROM i
44. 10 AS RIGHTS BEST S makes the string BEST now contain the word CORN verified by BEST TYPE VAL VAL converts a string to a double precision number 128 VAL D gives 128 STRS Conversely STRS converts a double precision number The sequence 567 STRS AS S makes the string AS equal to 567 Ll CI N LEN returns the current length of a string such as AS LEN lt return gt 3 MLEN MLEN returns the maximum length of a string such as AS MLEN RETURN 30 SUI UJ for example into text SUB allows substitution of characters in a string for example COWS EAT CORN AS S ATE 6 3 AS MIDS SUB replaces EAT with ATE in string AS S S adds strings together and puts the result in IB AND HAY BEST S AS BEST S BEST S adds BEST to AS Verify by BEST TYPE and get COWS EAT CORN AND HAY for example S S compares strings to see if they are equal in length and text If so a 1 is returned on the stack else a 0 APPENDIX J USER 24 HOUR CLOCK PROGRAM IN FORTH This appendix describes a 24 hour clock program written in FORTH using either machine level s Figure J 1 or interpretive interrupt see Figure J 2 handling The 24 hour clock is maintained under interrupt control using Timer 3
45. 4 2 1 DUP DROP SWAP and OVER The most common stack manipulation words are DUP DROP SWAP and OVER Let s explore these but first place some markers on the stack for reference DECIMAL 333 222 111 RETURN If we accidentally pull too many numbers from the stack we will know where we are Type S to check 5 RETURN 111 222 333 OK DUP pushes a copy of the top number onto the stack to create a new top number In sequence 123 DUP RETURN duplicates 123 on the stack then displays both numbers 123 DUP 123 123 OK DROP deletes the top number from the stack Try this with 456 789 DROP RETURN which deletes 789 and displays 456 789 DROP 456 OK SWAP exchanges the top two numbers on the stack Put two numbers on the stack 456 789 RETURN Use S to look at the stack S RETURN 789 456 LII 222 333 OK Now swap the numbers on top the stack and examine the stack with SWAP S RETURN which displays 456 789 111 222 333 OK Notice that the top two numbers are reversed Now try OVER which copies the Second item to be the new top OVER S RETURN 789 456 789 111 222 333 OK 4 2 2 Test and Duplicate with DUP A related word DUP duplicates the top number on the stack only if it is non zero otherwise DUP does nothing Continuing from the prior example type DUP S RETURN to show that the t
46. At run time REPEAT forces an unconditional branch back to just after the corresponding BEGIN At compile time REPEAT compiles BRANCH and the offset from HERE to addr n is used for error testing nil 12 n3 n2 m3 nl STACK rot Rotates the top three values on the stack bringing the third to the top e PRIMITIVE r p store Initializes the return stack pointer from user variable RO addr STACK r p fetch Leaves the address of a variable containing the return stack pointer WORD S0 SCCR SCDR SCSR SCR STACK NOTATION DEFINITION GROUP ATTR Bod ARITHMETIC s to d Extends the sign of single number n to form double number d addr PRIMITIVE U s zero Leaves the address user variable that contains the initial value for the parameter stack pointer See SP addr MISC P serial channel control register System address constant for addr of Serial Channel Control Register addr MISC P serial channel data register System address constant for addr of Serial Channel Data Register addr MISC P serial channel status register System address constant for addr of Serial Channel Status Register addr MASS s c r Leaves the address of user variable containing the screen number most recently refere
47. Bootstrap Program Load aa w mre wa e RERUMS dida a Mero MOHnTELOE bs ect iye REGULA o o FORTH Concepts Set ROatures Of PORTA a a A 3 2 Debugging a A my NEG A da ee a a Elementary Operations 421 Srmple ArYTJChme tiGOZzooelia A A 4 1 1 Examine Stack Contents with S 4 142 PERE from the Stack usStHg ux iie See te 4 1 3 Clearrng the Stack 2249 AARAU 4 1 42 Add L and SUDELAEE Sh ira eye ache or rur 4 1 5 Multiply and Divide 2e o mh 4 1 6 Postfix Notation and Stack Operation 4 1 7 Decimal and Hexadecimal Number Base 4 2 Stack Manipulation sonata REUS a ane I Ra 4 2 1 DUP DROP SWAP and OVER adds ds 4 2 2 Test and Duplicate with DUP 4 2 3 Delete the Top Stack Item with DROP 4 2 4 Rotate Stack Items with ROT 4 2 5 Copy d St ck ltem wrth PICK 2x e 4 3 Memory Operations Jv v EE SUE MS ER 4 3 1 16 B1t Store i and Fetch QG 34222 EA ad 453 2 8 Bity Store C and Fetch CQ ara iii Td Pa 2 2 2 2 2 Ps Hs Hs Hs Hs BA BRP HBP gt ge 1 2 5 3 5 9 O00 1 10 OSD nd Ce i C PO PO IE CO Section TABLE OF CONTENTS 1 6 DO LOOPS 1 5 Executing and Compiling using SOURCE Title 4 3 3 Initia
48. PROGRAM DESIGN CONSIDERATION Figure 8 3 Interpretive IRQ Interrupt Handling 8 4 A Unless modified by the user these vectors normally point to COLD so that an unintentionally generated interrupt will not totally crash the system 8 2 1 CODE Definition Form The form for an interrupt handler written as a CODE definition is HEX CODE lt name gt lt assembly code gt lt for interrupt gt lt handler gt RTI END CODE name 004X Set interrupt vector where X 0 or 2 Don t forget th END CODE as it completes the CODE definition and makes lt name gt available for use to load the interrupt handler address in the interrupt vector The word tick fetches the parameter field pointer address PFAPTR of the word lt name gt to the stack The PFAPTR obtained is a pointer to the starting address of the executable machine code The retrieves the actual address The 004X stores it in the appropriate vector 8 2 2 Code Fragment Form The form for a machine level interrupt handler written as a code fragment is HEX ASSEMBLER Include assembler vocabulary HERE Locate dictionary address assembler code for interrupt handling RTI 004X Store dictionary address in interrupt vector Since the interrupt handler is not named the starting address of the machine code
49. R COUNT DUP 1 R gt E SRE 34 STATE Q IF COMPILE WORD HERE C 1 ALLOT ELSE WORD HERE COUNT IB SWAP ROT OVER IB SWAP 1 CMOVE 2DUP 0 SWAP C THEN MMEDIATE VAL OVER BL SWAP C 1 NUMBER STR SWAP OVER DABS lt S SIGN gt MLEN DROP 1 Cf S DROP DUP 1 Cf ROT MIN 1 MAX 2DUP 0 SWAP C CMOVE LEN SWAP DROP MID SWAP gt R ROT MIN 1 MAX SWAP OVER MAX OVER 1 SWAP R gt 1 SWAP OVER SRCH MIN LEFT gt R gt R 1 SWAP R gt R gt MIDS Table I 1 FORTH String Words Continued RIGHTS gt R gt R 256 R gt R gt MIDS S ROT gt R ROT R gt SWAP OVER IB SWAP CMOVE SWAP OVER 25 CMOVE R gt 0 OVER IB SUI RO 5 MIN DUP gt R OV SWAP IB SWAP E J C IB SWAP T MIN 1 MAX CMOVE S RO T OVER IF 1 SWAP 0 DO DROP OVER ca SW 0 OVER CG IF 1 AP 1 SWAP 1 ELSE LEAVE THEN LOOP EL SE DROP 0 THEN SW SRCH and AP DROP SWAP DROP I 2 WORD DESCRIPTIONS Each of the string words are described below Note that there are two words and a variable area IB that are used internally by the
50. the difference of 0 less n pfa nfa DICTIONARY n f a Converts the parameter field address pfa of a definition to its name field address nfa addr MISC P N M I vector System address constant for addr of Low Level NMI vector flag COMPARISON not Leaves a true flag 1 if the number is equal to zero otherwise leaves a false flag Same as 0 addr d FORMAT number Converts a character string left at addr with a preceeding count to a signed double precision number using the current number BASE If a decimal point is encountered in the text its position will be given in DPL but no other effect occurs If numeric conversion is not possible an error message will be given 2 adear MASS U offset Leaves the address of user variable which contains a block offset to mass storage The content of OFFSET is added to the stack number by BLOCK Messages by MESSAGE are independent of OFFSE See BLOCK and MESSAGE d nl n2 n3 ARITHMETIC Tor Leaves the bit wise logical or of two 16 bit values WORD OVER PA PAD PG PD PF PFAPTR STACK NOTATION DEFINITION GROUP ATTR nl n2 nl n2 nl STACK over Copies the second stack value placing it as the new top of stack addr MISC P port a Syste
51. 16 22 SYN 36 54 d 23 ETB B 55 18 24 CAN 38 56 19 25 EM 39 97 1A 26 SUB 3A 58 IB 27 ESC 3B 59 TE 28 FS 3C 60 ID 29 GS 3D 61 E 30 RS 3E 62 IF 31 VS 3F 63 NUL Null SOH Start of Heading STX Start of Text ETX End of Text EOT End of Transmission ENQ Enquiry ACK Acknowledge BEL Bell BS Backspace HT Horizontal Tabulation LF Line Feed VT Vertical Tabulation FF Form Feed CR Carriage Return SO Shift Out SI Shift In APPENDIX H Block ASC CHARACTER SET HEX DEC ASC HEX DEC ASC 40 64 E 60 96 41 65 A 61 97 a 42 66 B 62 98 b 43 67 E 63 99 E 44 68 D 64 100 d 45 69 E 65 101 e 46 70 F 66 102 f 47 71 G 67 103 g 48 72 H 68 104 h 49 73 I 69 105 i 4A 74 J 6A 106 j 4B 75 K 6B 107 k 4C 76 L 6C 108 l 4D 77 M 6D 109 m 4E 78 N 6E 110 n 4F 79 0 6F 111 0 50 80 P 70 112 P 5l 8T Q Yl 113 q 52 82 R 72 114 r 53 83 S 73 115 S 54 84 T 74 116 t 55 85 U Tb XI 56 86 V 76 118 V 57 87 W 77 119 W 58 88 X 78 120 X 59 89 Y 79 121 y 5A 90 Z 7A 122 Z 5B 91 7B 123 5G 92 7C 124 5D 93 7D 125 5E 94 1 7E 126 5F 95 e 7F 127 DEL DLE Data Link Escape DC Device Control NAK Negative Acknowledge SYN Synchronous Idle ETB End of Transmission CAN Cancel E End of Medium SUB Substitute
52. 3S SCR H 77 C COMPATIBILITY WORDS FOR RSC FORTH 3 4 25WAP ROT OR ROT R 3 2 LOAD DUP BASE SWAP DECIMAL S R BASE LOAD 3 3 THRU 4 SUAP DO I LOAD LOOP 5 4 B BUF 4824 3 64 UC L PAD HERE 68 5 5 6 7 8 9 Figure 0 1 RSC FORTH Editor Continued 0 7 X X X X X OX OX OX OX KEKE HR OX Xx X X X 0X X X OX OX OX X CX X X X KE WOX X X X 0X 0X 0X 0X 0X 0X X 0X 0X X This page is intentionally left blank Anderson A and Wasson P FORTH 79 Tutorial and Rel Blvd Suite 506 West Los Angeles CA February 1981 1 2077 Wilshire Cassady J J Bartoldi Language Brodie L P for St Stepwise Data Acquisi Symposium and Course on Min Development a tarting FORTH Stacking Strings in FORTH PPE EL ECTE BL OGRAI PHY nd Inst ion and i and Microcomputers and their Applications Prentice Hall Debugging Using a Small trument Control ference Manual MicroMotion Well Structured Interactive Proceedings of the International Kal 1981 nglewood Cli BYT FES No E February 1981 pages 152 162 Deane R A Proposal on Strings for FORTH Dr Dobb s Journa
53. 4 10 2 VARIABLE VARIABLE is like CONSTANT but the word it creates returns the address of a value instead of the value itself Therefore new values can be stored into the variable Try 50 VARIABLE Y Define variable Y initialize to 50 Y RETURN 50 Fetch and print Y 60 Y Store 60 into Y Y RETURN 60 Fetch and print Y Although this example illustrates the use of the word VARIABLE to initialize the value to 50 the better practice is to always create the variable as zero or some dummy value and initialize if necessary in an initialization section of the code If the program is later moved to ROM the variable location will have to be in RAM where it cannot be initialized at compile time s Section 4 10 4 4 10 3 Defining Words CONSTANT and VARIABLE are both in a special class of words called defining words Defining words add new words to the dictionary The only other defining word we have seen so far is the colon used to begin colon definitions As with the colon the names created by CONSTANT and VARIABLE can be up to 31 characters long and can redefine other names The RSC FORTH system includes eight defining words which are commonly used the colon CONSTANT VARIABLE USER VOCABULARY CODE
54. HEX F7 01 AND RETURN 1 08 01 OR RETURN 9 F7 01 XOR RETURN F6 The word NOT is provided as a synonym for 0 see Section 4 7 2 to improve readability in logic expressions Note that NOT is not a bit wise operation it is only a Boolean inversion and just returns the right most bit of the word To negate all the bits of a word i e to take its one s complement use 1 XOR For example HEX AAAA 1 XOR lt RETURN gt 5555 AAAA FFFF XOR lt RETURN gt 5555 These logical operations can also be applied to truth values returned by comparisons in this case only the right most bit of each word is important For example suppose that a word HOT has already been defined to return a value of true if a sensor detects a temperature higher than a pre set limit false otherwise Also suppose that a voltage value is previously stored on the stack The test 8 gt HOT OR will return true if the voltage on the stack is greater than 8 or the temperature is high or both In this example the voltage value on the stack is first compared to 8 by use of the relational operator This results in a Boolean value left on the stack Then HOT puts another Boolean on the stack and the two Boolean values are OR ed together Note that HOT 8 gt OR would be erroneous in this case because the Boolean left on the stack by HOT would be compared with the 8 and the re
55. NULL FOUND 601 OF CHARACTE 600 C FOR TYPE M PRINT MESSAGE 600 COUNT 30 MIN TYPE D DECIMAL M T T SET TIME 100 U GET SEC 100 MOD MIN HRS TICKS C LOAD HRS TICKS 1 C LOAD MI TICKS 2 C LOAD SE O TICKS 3 C ZE C CONTINUOUSLY DIS BEGIN 24 EMI BLANK N C RO 100TH SEC CURSOR PLAY MSG amp TIM EC E 13 EMI STAY ON SAME LINE D T UNTIL 23 EMI RESTO RE CURSOR QU D DISPLAY MSG amp TI CR D QUIT Fi E ONCE Using an ERMINAL JE gure J 2 24 Hour Clock Program Interpretiv Interrupt Handler Cont d J 6 APPENDIX K UTILITY EXAMPLES T K I MEASURING FORTH WORD EXECUTION TIME It is often desired to know how long it takes for a FORTH word to execute especially in time critical applications The following words measure such execution time in R65F11 or R65F12 clock cycles i e microseconds HEX ON FF FF 1C C Ez vr OFF 001C 8 12B CR FFFF SWAP 0 D The word ON initializes and starts Timer B The word OFF displays the number of cycles elapsed from the start of the timer minus ON and OFF word overhead Use these words as shown in the follow
56. ON DEFINITION GROUP ATTR SECURITY if the stack is Issues error message 7 FULL STACK out of bounds INPUT OUTPUT flag Tests the terminal keyboard for actuation of any key Generates a Boolean value A true flag 1 indicates actuation whereas a false flag 0 indicates non actuation addr n MEMORY fetch Leaves the 16 bit contents of the address on top of the stack SECURITY abort Clears the stacks and enters the execution state Returns control to the serial keyboard IHMETIC Tri i AR absolute Leaves the absolute value of n as u addrl addr2 I O addr2 in ASC format in as necessary Dumps bytes from addrl to as many semicolon records Also sends closing record addr n compile time CONTROL again Used in a colon definition in the form BEGIN AGAIN At run time AGAIN forces execution to return to the corresponding BEGIN There is no effect on the stack Execution cannot leave this loop unless R gt DROP is executed one level below WORD AGAIN Cont ALLOT ALLOT AND ASSEMBLER AUTOSTART B BUF STACK NOTATION DEFINITION GROUP ATTR At compile time AGAIN compiles BRANCH with an offset from HERE to addr n is used for compile tim
57. PROM programmer loops and other utilities can likewise be picked out of the codes area before final preparation for a ROM code he question of whether a particular word is in or out of the kernel can be uite important when preparing target standalone programs No references can be ade to words defined in the Development ROM if the program is to stand alone hecking the CFA of a word to be used in a definition can be tedious The word KERNEL followed by a word name performs a quick check KERNEL responds with a simple IN or OUT message indicating location 908 0 H 6 3 5 Preparing for Autostart After a program is target compiled and thoroughly tested just prior to being transferred to EPROM you may want to prepare it for autostart of your program on power on reset In order to do this a A55A pattern must be placed on a 1K byte boundary followed by the PFA of the word to be started This will usually be the first four bytes of your final EPROM The word AUTOSTART was added to RSC FORTH to simplify the process To use AUTOSTART the address of the 1K boundary being used must be on the stack AUTOSTART should be followed by the high level FORTH word that defines th ntire process to be run A strong word of caution is in order AUTOSTART should be used with care Once it is executed there is no way to return the Development ROM using a reset Try the following example to see
58. Register can be examined in the IRQ interrupt routine to determine that the IRQ was generated by the Counter A Underflow While the Timer is operating in the Interval Timer Mode PA4 operates as a PA I O bit A timing diagram of the Interval Timer Mode is shown in Figure 9 5 Pulse Generation Mode In the Pulse Generation mode the CA line operates as a Counter Output The line toggles from low to high or from high to low whenever a Counter A Underflow occurs or a write is performed to address 001A The normal output waveform is a symmetrical square wave The CA output is initialized high when entering the mode and transitions low when writing to 001A ATA Ads o hs COUNTER UNDERFLOW cowe 5 I 7 I ama COUNTER INTERRUPT ENABLED SET ANY TIME BEFORE COUNTER UNDERFLOW FLAG COUNTER UNDERFLOW TRO Ho rueneim sm ae Figure 9 5 Interval Timer Timing Diagram Asymmetric waveforms can be generated by changing from Pulse Generation to Interval Timer mode after only one occurrence of the output toggle condition c Event Counter Mode In the Event Counter mode CA is used as an Event Input line and the Counter decrements with each rising edge detected on this line The maximum rate at which this edge can be detected is one half the 02 clock rate The Counter can count up to 65 535 occurrences before underflowing As in the other modes
59. SPACI SPACI SWAP GI El n TOGGLE TYPE U U lt UC L UPAD UR W XOR FCD4 F7A5 F6CE F7C5 F8FO F98F FAAC E7 E7 3F 3F F6FD F8 OC F8CD F9 FC 74 2C F8CA FD FE E11 43 6C F6F3 F 6 F9 FE EA 9D 3A F7D3 F8C7 F8 F9 F6 F6 F9 F8 F8 F8 F6 30 3F 46 7B 40 DO D3 D6 DC SECTION 3 FORTH CONCEPTS FORTH is quite different from more conventional languages such as BASIC FORTRAN or Pascal It creates a computing environment with unique strengths tools and styles Some of the structures of FORTH have little correspondence with those of other languages This overview of the language and the RSC FORTH implementation provides background for the how to do it chapters which follow 3 1 FEATURES OF FORTH FORTH is EXTENSIBLE meaning that you add your own operations to the language New words operations are defined in terms of previously defined words or assembly language until a single word represents th ntire user s program The program word can then b xecuted by typing its name or made to auto start upon reset Except that your words may be defined in RAM or user provided PROM or ROM there is no distinction between your new operations and those originally part of the language Extensibility allows users to define libraries or even thei
60. double dividend Unsigned divide leaving double quotient and remainder from double dividend and single divisor Maximum intermediate A 3 ARITHMETIC AND LOGICAL Continued MIN nl n2 min Minimum and a 3 3 Set sign n3 nl times the sign of n2 D dal niSs d3 Set sign of double number ABS n absolute Absolute value DABS d absolute Absolute value of double number NEGATE nis gt h Change sign DNEGATE Cd gt Sd Change sign of double number S gt D n d Sign extend single number to double number 1 Al unes Increment by 1 nl n14 2 Increment by 2 1 rb gt miser Decrement by 1 2 nl nl 2 Decrement by 2 AND nl n2 and Logical AND bitwise OR nl n2 Ot Logical OR bitwise XOR nl n2 xor Logical exclusive OR bitwise BCD ul u2 Connect a number to its BCD equivalent BOUNDS addr n Convert start addr and addr r n addr count to start and stop addresses A 4 COMPARISON OPERATORS lt nl n2 f True if nl less than n2 gt pb NA te True
61. io SP U SO URCE T F ERMINAL IND LOOP EX ECUTE In the following descriptions a FORTH word comprising of letters and numbers is written in upper case Since some FORTH words contain special characters that may be confused with sentence structure e g periods commas or apostrophes the FORTH words are set off by spaces e g S These single spaces are not part of the FORTH word and should not be entered 4 1 SIMPLE ARITHMETIC FORTH arithmetic like that of advanced pocket slide rule calculators uses a stack to store operands and results Operations such as add subtract multiply and divide take their arguments from the stack and return their results to it To see how the stack works give FORTH a cold restart by typing COLD and pressing the RETURN key The system will display RSC FORTH VI 6 Now type the following five numbers 1 22 333 44 5 and terminate the input by pressing the RETURN key RETURN at the end of a line signals that your input is complete The RETURN is shown in the initial examples but is not shown in later examples except where needed to clarify data or command entry Be sure to insert one or more spaces between each number Now the numbers 1 through 5 are separate numbers stored on the stack with 5 at the top FORTH responds to your input by dis
62. of the R65F11 or R65F12 The program allows you to initialize the clock enter a message that will be displayed with the time and display the time just once or continuously J 1 HOW TO OPERATE THE PROGRAM The 24 hour clock program is compiled into FORTH words as described in the next Section Once compiled you must be in FORTH to command the 24 hour clock functions Once initiated however the clock will continue to run as long as it is not reset Timer 3 operating mode is not altered or the processor interrupt enable bit and the Interrupt Enable Register IER are not altered to inhibit the IRQ interrupt The 24 hour clock functions are entered from FORTH using any of four keys These four keys are defined as FORTH words and are entered into the FORTH vocabulary The keys their functions and the associated operating procedure is M Key Allows a message of up to 32 characters to be displayed preceding the time value Enter the message as follows 1 Type M 2 Press RETURN 3 Type a message up to 30 characters long 4 Press RETURN do not press RETURN if exactly 30 characters are entered An example is M RETURN RSC FORTH TIME RETURN OK T Key Allows the initial time value to b ntered Enter it as follows 1 Type in the time in the format HH MM SS not HH MM SS 2 Press SPACE 3 T
63. subroutines are necessary But if full machine speed is needed allows machine language subroutines assembly source has been typed in o separate assembly and linking passe in assembly language IF ELSE and define their own macros and use th and other assembly time utilities modes are available This one pass illustrating the compactness of FOR The routines created by this assemb regular FORTH definitions The user assembly language Therefore an ap high level using FORTH words and converted to assembly language code ic registers A X Y etc in the R6502 CPU routines FORTH can do anything machine t enough that usually no assembly language RSC FORTH includes an assembler It also to be tested immediately as soon as the r otherwis ntered with no waiting for s It encourages structured programming even BEGIN UNTIL macros are provided Users can e full power of FORTH for address arithmetic All R6502 and R65110 op codes and addressing assembler is implemented in about 1 5K bytes TH s object code ler have FORTH names and behave exactly like needn t know which words are programmed in plication can first be written entirely in if more speed is necessary parts can be with no changes required elsewher 3 2 FORTH code is extremely TRANSPORTABLE between machines It is common for substantial programs to be moved between d
64. text 3 DELIM TEXT FIND BUF BUF MOVE SEEK s F C text find 8 display J CF 3 3 Figure 0 1 RSC FORTH Editor Continued 0 3 KAR KK CK OK OK C OX KKK OX CX X KK OX X X 0X XX ET KEK X X A OS DA CDBGDm GOQwousgtuoG Le t 3S SCR Y leoForth editors D Till U 24 FEB 83 MWR TEGE C text delete from cursor SCR H 67 leoF RTH Editor Bump S 24 FEB 83 MWR 3 VARIABLE COUNTER BUMP C bump line handle paging 3 4 COUNTER COUNTER 56 gt IF COUNTER CR CR 45 MESSAGE 42 EMIT THEN 3 8 end global search print hits 42 EMIT DEL Ihn TEXT COUNTER FIND BUF BUF MOVE SCR DUP DR DO I SCR TOP BEGIN 1L INE IF SCR 4 R BUMP THEN 4823 RH G lt UNTIL TERMINAL IF LEAVE THEN LOOP R gt SCR 3 SCR N 68 leoFORTH Editors I R M 24 FEB 83 MUR 1 t text insert within line J DELIM TEXT INSERT BUF BUF MOVE INSERT BUF COUNT SLAG ROT OVER MIN DR R RH R 2R DUP HERE R CMOVE HERE ULEAD R CMOVE R gt CMOVE UPDATE 5 R C text replace matched w insert E 2 E LEAD DEL TM TEXT FIND BUF BUF MOVE ALINE IF SEEK ERROR THEN ULEAD SWAP CDELETE a 3 C text put text under cursor line C L RH SPREAD P 3 L erase backwards from cursor FIND BUF QQ CDELETE 7 3 C text find it kill it show result Cre E 1 swap find insert buffers to match FIND BUF PAD 65 CMOVE INSERT BUF FIND BUF 6S CMOVE
65. the Counter A Underflow bit IER4 is set to logic 1 if the underflow occurs See Figure 9 6 d Pulse Width Measurement Mode This mode allows the accurate measurement of a low pulse duration on the CA line The Counter decrements by one count at the 02 clock rate as long as the CA line is held in the low state The Counter is stopped when CA is in the high state The Counter A underflow flag is set only when the count in the timer reaches zero Upon reaching zero the timer is loaded with the latch value and continues counting down as long as the CA pin is held low After the counter is stopped by a high level on CA the count holds as long as CA remains high Any further low levels on CA will again cause the counter to count down from its present value The state of the CA line can be determined by testing the state of PAS A timing diagram for the Pulse Width Measurement Mode is shown in Figure 9 7 e Serial I O Data Rate Generation As mentioned earlier Counter A also provides clock timing for the Serial I O which establishes the data rate for the Serial I O port When the Serial I O is enabled Counter A is forced to operate at the internal clock rate Counter A is not required for the Receiver S R mode The Counter I O PA4 may also be required to support the Serial I O Table 9 4 identifies the values to be loaded in Counter A for selecting standard data rates with a
66. ugh tt mmediate because almost all FORTH words can be executed directly as commands fr same in this mode as when compiled required can simply be typed onto t other operations and results can b each component of the new definitio keyboard to aid in debugging FORTH debugging seldom requires exa being tested Documentation of the form is required i e inputs out their code to be listed Fewer list program development than with other is directly in front of you FORTH allows easy MACHINE ACCESS u memory and 1 0 data ports and cont un time protection can be implemen r user words to include run time b om the keyboard and will behave exactly the into later definitions Any arguments he stack before the test or generated by e observed or printed immediately Usually n can also b xecuted interactively from the mining any code except the single definition behavior of the defined words in glossary puts and actions but there is no need for ings are therefore required during FORTH languages Everything you need to work with nlike most other high level languages All of rol registers can be addressed although ted simply by redefining appropriate system ounds or other checks during testing Except hich require assembly language sub anguage can do And FORTH runs fas f O for direct access to machine specif WwW T
67. 0060 to 00A0 are usually safe since normal stack depths do not exceed 16 words at a time 11 1 The print functions such as eae DAR etc make use of the area of PAD and therefore must use external RAM at 0300 The terminal input routines such as QUERY EXPECT etc use the Terminal Input Buffer TIB at address 0380 For these and other applications that require disk operations or large block of memory external RAM is a must he R65FR1 Development ROM initializes RSC FORTH to start its dictionary at 0400 the first 1K byte boundary If no RAM is required in the final system nd the program is small i e less than 1K bytes the RSC FORTH development ystem can be as simple as the one shown in Figure 2 2 The program can then be e veloped in the RAM and dumped to a PROM programmer After PROM programming e RAM device can be removed and replaced with the PROM such as a 2716 Only he last half of the PROM would be used but this would still be a very cost ffective solution T a S d t e If RAM is required in the final system or more than 1K byte of program is to be generated an additional RAM will have to be added to the development system shown in Figure 2 2 Decoding logic will also need to be changed accordingly The program will be developed in the second RAM at address 0800 to SOFFF and replaced with a EPROM
68. 02 clock rate of 1 MHz and 2 MHz Although Table 9 4 identifies only the more common data rates any data rate from 1 to 62 5K bps can be selected by using the formula 2 16 x bps Figure 9 6 Event Counter Mode Figure 9 7 Pulse Width Measurement 9 15 where N decimal value to be loaded into Counter A using its hexadecimal equivalent 2 the clock frequency 1 MHz or 2 MHz bps the desired data rate In Table 9 4 rate may be s are acceptabl rates which f you will notice that the standard data rate and the actual data lightly different Transmitter and receiver errors of 1 5 or less e A revised clock rate is included in Table 9 4 for those baud all outside the limit Using a 2 4576MHz will give accurate Baud rates 9 3 2 Counter Counter B con follows Low Upper Latch B sists of a 16 bit counter and two 16 bit latches organized as er Counter B LCB Upper Counter B UCB Lower Latch B LLB ULB Lower Latch C LLC and Upper Latch C ULC Latch C is used only in count of eith selected Th location 001D Counter B A Latch B conta by executing at location 0 the asymmetrical pulse generation mode The counter contains the er 22 clock pulses or external events depending on the counter mode e contents of Counter B may be read any time by executing a read at for the Upper Counter B and at location 001E or 001C
69. 1 the IRQ or NMI code fragment 2 the ARM word to rearm the interrupt etc 3 the ENABLE and DISABLE words for IRQ if using IRQ A colon definition level FORTH word is also required to run at interrupt request The last word executed by this word is ARM above b See that NMI and IRQ do not contend for the interpretive interrupt there is no stacking and they can get lost Ex Do not alter any of FORTH s floating buffers at HERE and PAD or any of the USER variables BASE DPL IN etc or leave anything on the stack between interrupts Use caution when using interpretive interrupts think the sequence through before acting If it does not operate correctly perhaps you are overwriting something that FORTH needs Try using a do nothing word like GI DUMMY ARM SMUDGI for the interpretive interrupt word and see if that works The X register contents must be saved if X is used during the interrupt processing but not in XSAVE or any of the other regular FORTH registers For example use the Return Stack instead such as TXA PHA This Page is intentionally left blank SECTION 9 PROGRAMM NG THE R65F11 MICROPROCESSOR O IN FORTH Programming the R65F11 and R65F12 single chip microcomputer I O functions in FORTH is similar to programming individua
70. ARRAY 298 ALLOT To fetch the nth value of this array one can use GETN ARRAY SWAP 2 Q Type 41 GETN to place the value of the 41st element onto the stack T ulated To define an array 4 11 CHANGING THE NUMBER BASE We have already seen the words DECIMAL and HEX pectively FORTH can work in any number base even above 16 but in practice only 10 16 2 and perhaps 8 are commonly used 10 and 16 res which set the number base to The number base can be changed by storing the desired base value into the user which is available as part of the system For example variable BASE 2 BASE sets FORTH terminal input and output to binary The do this BINARY 2 BASE and then later just execute BINARY user could define a word to The words DECIMAL and HEX similarly change BASE for convenience thes words are already defined in the system as supplied Note that BASE only affects input and output Internal computation is always in binary so there is no computation speed penalty for using different bases Also note that the base will remain as set until changed again You can easily determine the current I O number base with BASE DUP DECIMAL The word puts the value of BASE on the stack valu
71. B but vary one or more of the parameters until you of the described FORTH word As you are learning FORTH you message to be displayed or cause th for the error definition and s up or run away press the RES then try the example again Yo recover th xample initialization Section 5 5 but leave that for ed by performing the following procedure As each new FORTH word is encountered in this section read the explanation and perform may make errors that either cause an error uggested recovery ET key to reinitial e microcomputer to hang up or to run away If an error occurs with a displayed error message or number refer to Appendix E If the program appears to hang lize the microcomputer You can u may have to back up a few steps however to 40B 3375 3358 3301 S d IF 32A9 3294 3149 306E 304B UNTIL THEN AUTOSTART DREAD 3017 2E99 B SCR LOAD 2ED7 2DBF LINE BUFFER I FI 2D15 2CF9 2CD9 2CB9 2BF9 M MOD M ABS ONS 2AB2 298B B 2877 2836 27E6 2795 2753 26F8 2646 25F7 25D3 25BA 2575 2524 2507 24 24 24 D4 A7 71 24 02 DP 1 C L STATI BLK VOC LINK V
72. C L DUP INSERT BUF C CMOVE 3 CKILL C line erase line to blanks LINE C L BLANKS UPDATE 5 C SPREAD C spread block at cursor line LINEH DUP 4 44 DO I LINE I 4 MOVE 4 LOOP CKILL 3 C print cursor line 2 CR SPACE HLEAD TYPE CURSOR LAG TYPE gt LINEM 3 R CDELETE C H zap H chars before cursor R ULAG R LAG R NEGATE RH ULEAD SWAP CHOVE R BLANKS UPDATE 3 gt gt C U move cursor H characters RH 7 SCR Y 64 leoForth editor X T L N B TOP R P 24 FEB 83 MUR x C delete cursor line save in i buf J gt LINER DUP HOLD 4S DUP ROT DO I 4 45 MIN LINE I MOVE LOOP KILL 3 T C line type a line move cursor C L RH T 3 iH Ee jJ list current screen SCR LIST 3 TOP O RH E C reset cursor to home J N 4 SCR TOP 3 C move to next block B 4 SCR TOP 3 C move to prev block CPUT C replace cursor line w i buf J gt LINER INSERT BUF 4 SWAP MOVE 3 P C text put text to cur line i buf DELIM TEXT INSERT BUF BUF MOUE PUT 3 SCR N 65 leoForth editor searching 24 FEB 83 MWR 3 SEEK ERROR t error handler for failed search J TOP FIND BUF COUNT TYPE QUIT 3 ALINE 4 sean for find buf give success ULAG OVER gt R FIND BUF COUNT MATCH R RU B E CSEEK find buf over whole block or err J BEGIN 1023 RH G lt IF SEEK ERROR THEN 4LINE UNTIL 3 CF E text 1 find
73. FSC Escape FS File Separator GS Group Separator RS Record Separator US Unit Separator SP Space Blank Delete H 1 APPENDIX FORTH STRING WORDS This appendix defines FORTH words that can be created to handle character string data The defined words are based on and extend functions described by Ralph Appendix N 1 1 WORD COLON DEFINIT The following string ha definitions listed in T FORTH Word ONS Deane in an article entitled A Proposal On Strings for FORTH published in Dr Dobbs Journal of Computer Calisthenics amp Orthodonia November December 1980 See ndling words can be implemented using the colon able 1 1 Function STRING Define a string y Enter text S Store entire string SUB Substitute part of string MIDS Get m characters of string LEFTS Get left most n characters of string RIGHTS Get right most n characters of string VAL Convert string to numeric value STRS Convert numeric to string LEN Get current length of string MLEN Get maximum length of string S Add strings Compare strings Table 1 1 FORTH String Words SRCH DUP BEGIN DUP C SWAP 1 SWAP END SWAP 1 STRING lt BUILDS ABS 255 MIN 1 MAX DUP C 0 DO 32 C LOOP 0 C DOES 1 DUP SRCH O VARIABLE IB 254 ALLOT Table I 1 FORTH String Words Continued
74. Figure 9 4 When parity is disabled the 5 6 7 or 8 bits are terminated with two stop bits When parity is enabled words with 4 6 or 7 bits end with two stop bits Those with 8 bits are allowed only one stop bit To calculate a desired baud rate in FORTH enter the following DECIMAL 1000000 means double precision 16 9600 U DROP 1 Instead of a final print command enter HEX 18 to establish the baud rate Table 9 4 Counter A Values for Baud Rate Selection ASYNCHRONOUS OO AA PA oor Gate Cate e Oates ASTNCHRONOUS MODE WITH PARITY oor DATA rer pate om cata PFT REGISTER MODE OT Data wono u Sear AECA TEA CLOCHE Pad na P Figure 9 4 Serial Communication Bit Allocations 9 10 In the Shift Register Mode eight data bits are always used The serial data is shifted out via the SO output on pin PA6 as it is in the asynchronous mode The serial clock however is available at the CA line PA4 only in the transmitter shift register mode The receiver and its selected control and status functions ar nabled when th SCCR Bit 6 is set to a 1 In the asynchronous mode incoming words must have one start bit the propa s number of data bits and parity and one stop bit Framing error over run and parity error conditions or a Receiver Data Register Full condition will set the appropriate bits in the Serial Channel Status R
75. INSERT BUF BUF MOVE 5 Figure O 1 RSC FORTH Editor Continued 0 4 3S xe EKEKR OX KEK OK OX OX OX KE X X Ck X OK 0X OX KKK KK OX X X X Ck X RR KKH KKK KK KK a 4 2 3 4 5 6 7 8 9 18 11 12 13 44 45 0 ON 0 0 5 0 IN o 9 SCR 69 SCR y 78 C leoeditor NEU UFR s hyperhack version 24 FEB 83 MUR 3 NEW FORTH C CUR FORTH C CUR 3S C linet 3 16 0 DO CR I 3 R SPACE I OVER IF C DROP J TIB C L EXPECT B IN 4 WORD HERE 4 CG 1F 1 RENT Q CONTEXT J C L RH NLAG BLANKS HERE COUNT BLAG DROP SWAP CMOVE UPDATE 4 ELSE 8 EMIT C ROT 2 J THEN I SCR Q RENT CONTEXT J LINE THEN LOOP DROP 1 SCR H 74 C high level pseudo TEXT and MATCH 24 FEB 83 MUR s TEXT Ca1H a2 f f s SIGN INCORRECT SWAP DUP IF R 8 ROT ROT R BOUNDS DO DUP CQ I Ce DUP IF ROT DROP SWAP LEAVE ELSE DROP 4 THEN LOOP DROP ELSE DROP THEN 3 MATCH C a4 84 02 42 f a3 scan for a string R R 2DUP R R 2SUAP BOUNDS DO 2DUP FORTH I TEXT IF I R 2DROP DROP R 8 8 LEAVE THEN LOOP 2DROP OVER 5 18 Figure 0 1 RSC FORTH Editor Continued 0 5 X X KEK KKK KKK EE Hrs e d Uj 50 mG O00WwWwoueuN et 000x096 0MP gt UN As O SCR N 72 C EDITOR 42 bulkclear wipe 24 FEB 83 MUR 3 BASE HEX WIPE C screenl wipe screen J OFFSET FLUSH PAD 1824 BLANKS PAD PAD SWAP 8 R U BULKCLEAR C from scr 2 to ser 5 J CR 4 SWAP DO FORTH I EDITOR
76. Insert ASC character into output string Hold pointer user variable Suppress trailing blanks Display line of text from mass storage Count and address of message text Print number ASC string right justified in field Print double number ASC string Print double number ASC string right justified in field Address of number of digits to the right of decimal point A 9 MONITOR COLD MON CLD WRM addr SOURCE FINIS XON mm XOFF A 10 COMPILER TEXT INTERPRETER PS e Re COMPILE lt name gt LITERAL on n DLITERAL do e d EXECUTE addr Ca gt MMEDIATE name NTERPRET STATE addr A 11 DICTIONARY CONTROL CREATE FORGET name HERE addr ALLOT op RA i TASK sss y name addr FIND found name PFA b tf name not found name ER RSC FORTH cold start Exit to RSC FORTH Monitor User variable containing the COLD WARM flag When equal to A55A reset does warm start otherwise does cold start Interpret input from active input device with XON XOFF protocol End of file marker for input via SOURCE Restores input vector Emi
77. Monitor when making field modifications to existing products based on RSC FORTH Table 2 1 Parameter Field Addresses RSC FORTH Kernel Words with their i S LOOP MOD 0 0 lt O OBRANCH 2DROP F858 2DUP F7EF D FE7D 3 FSBB D FE5C 4 F8BF D R FEAO0 S F717 DABS FADO F954 DECIMAL FA31 lt FE52 DIGIT F4F8 F938 DISK F535 F96C DNEGATE F4AF gt R F734 DPL FBO6 FEEC DREAD FCB6 TERMINAL F60A DROP FCE8 F83B DUP FCDC ABS FCAE DWRITE F778 AND F6BE EEC F818 BANKC FFA2 EMIT FC36 BANKCQ FF4A ENCLOSE F96C BANKEEC FF52 ERASE F9A5 BANKEXECUTE FF5A EXECUTE FAOB BASE F8D9 EXPECT FEE4 BL F8C3 FILL FED8 BLANKS FAEC HEX FCCA BOUNDS F803 HLD FCBE BRANCH F480 HOLD F8AF C F868 IN F76B C L F8E8 INIT F7A5 CQ F84B KEY F497 CLD WRM F8DC LEAVE F8B3 CLIT F458 L1T F8F8 CMOVE F626 M F913 COLD FB48 M F8B7 COUNT F9E3 M MOD F820 CR F613 MAX F920 D F787 MIN F7D1 MOD NEGATE tU D UO EH QUERY RP RP RO ROT S gt D S0 SP SPG
78. N hasn t reached zero xecution returns to BEGIN When N reaches zero after executing TICK DEC 6 times execution continues ahead after UNTIL Note that BEGIN generates no machine code but is only an assembly time locator In this example 0 UNTIL generated a BNE instruction to the address located by BEGIN 7 6 2 Conditional Execution Paths of execution may be chosen at assembly in a similar fashion as done in colon definitions In this case the branch is chosen based on a processor status condition code The general format is using 0 as a typical condition code word PORT LDA 0 IF code for zero set THEN continuing code In this example the accumulator is loaded from PORT The zero status is tested and if set Z 1 the code for zero set is executed Whether the zero Status is set or not execution will resume at THEN The conditional branching also allows a specific action for the false case Here we s the addition of the ELSE part PORT LDA 0 IF lt assembly code for zero set gt ELSE lt assembly code for zero clear gt THEN lt continuing assembly code gt The test of PORT will select one of two execution paths before resuming execution after THEN The next example increments N based on bit D7 of a po
79. NOTATION DEFINITION GROUP ATTR addr n add n addr ARITHMETIC bounds Bounds is equivalent to OVER SWAP It is used to convert addr and count to a start and stop address for a loop PRIMITIVE branch The run time procedure to unconditionally branch An in line offset is added to the interpretiv pointer IP to branch ahead or back BRANCH is compiled by ELSE AGAIN and REPEAT n addr MASS buffer Obtains the next block buffer assigning it to block n The block is not read from mass storage If the previous contents of the buffer is marked as UPDATED it is written to the mass storage If correct writing to mass storage is not possible an error condition exists The address left is the first byte within the buffer for data storage n addr MEMORY c store Stores the least significant 8 bits of n into the byte at the address a DICTIONARY c comma Stores 8 bits of n into the next available dictionary byte advancing the dictionary pointer b lt name gt compile time DEFINING P name b run time c comma constant A defining word used in the form b C CON name to create a dictionary entry for name leaving b in its parameter field When name is executed later in command mode b will be pushed on the stack when in compile mode the CFA of CLIT foll
80. Section 4 11 This section covers the special situation of accepting a numeric string as input and interpreting it as a number Such special input is seldom necessary because most programs can accept input from the FORTH system itself i e numbers typed onto the stack if they use a terminal at all This special terminal input is most often for turnkey programs not run under the direct control of FORTH in which the user should not see the OK First use EXPECT to accept a string from the user s Section 4 11 2 Then use NUMBER to interpret part or all of that string as a number the parentheses are part of the name This operation is a bit complicated It needs a double precision zero on the stack as well as the address of the first ASC character of the number minus one i e the address of one byte befor the number begins This address must be on top of the stack NUMBER then returns the value of the number it is accumulated into the double precision zero The address on top of the stack is incremented to point to the first non numeric character i e to the terminator of the number the program may test this terminator which would normally be a blank and if it is an unexpected quantity e g a letter erroneously typed by the terminal operator error handling can be performed For example INPUT 600 10 EXPECT 00 600 1 NUMBER de
81. Symbol Definition nyni reee Opals ss u ul no ud udt s s addr addrl b c f ff tf STACK DUP 2DUP DROP 2DROP SWAP OVER ROT DUP 16 bit signed number 32 bit signed number 16 bit unsigned number 32 bit unsigned number address 8 bit byte with eight high bits zero 7 bit ASC character value with nine high bits zero Boolean flag zero false non zero true Boolean false flag value zero Boolean true flag value non zero MANIPULATION n nn Duplicate the number on the stack d dd Duplicate the top double or nl n2 number or the top two nl n2 nl n2 numbers on the stack Cones 3 Delete the top number on the stack d Delete the top double or nnl n2 number or the top two numbers on the stack nl n2 n2 nl Exchange the top two numbers on the stack nl n2 Copy second number on nl n2 nl the stack to the top nl n2 n3 Rotate the third number n2 n3 nl on the stack to the top n Duplicate the top number on the stack only if it is non zero A 1 A 3 STACK MANIPULATION Continued gt R n R n R n PICK n nth SP addr RP addr S FS SP NUMERIC REPRESENTATION DECIMAL HE BASE
82. T Assembly time R T Run time H B High byte L B Low byte addr addrl Address C I OP CODES ADC DEC LSR SEC AND DEX NOP SED ASL DEY ORA SEI BIT EOR PHA SMB BRK INC PHP STA CLC INX PLA STX CLD INY PLP STY CLI JMP ROL TAX CLV JSR ROR TAY CMP LDA RMB TSX CPX LDX RTI TXA CPY LDY RTS TXS SBC TYA E Ca Es 2 3 4 ADDRESS MOD A QX y Y X Y CONDITIONAL 0 A T 02 A T VS A T CS A T NOT A T BITCLR A T BITSET A T CONTROL BEGIN UNTIL AGAIN ES E Accumulator address mode Immediate address mode Indexed X address mode Indexed Y address mode Indexed Indirect Indexed Y address mode Indirect Absolute address mode Indirect X address mode SPECIFIERS eee Branch on negative N 1 Ce Branch on zero Z 1 QC Branch on overflow V 1 neveu Branch on carry C 1 COL 962 Reverse the condition code n addr cc Branch on bit n of zero page address addr clear n addr cc Branch on bit n of zero page address addr set A T addr 1 At A T leaves the dictionary address and the value 1 pointer for later testing of conditional pairing R T At R T marks the beginning of a repeatedly executed assembly sequence A T add
83. TRUE MILES CENTS GAL and MPG It is not necessary but a convenience to use two memory storage locations in this calculation one constant for k and a variable where we can store the current odometer reading ml to use as the last odometer reading m0 for the next calculation Start with the word MPG and use the normal FORTH output formatting words except include a decimal point in the output text string with the phrase 46 HOLD and embellish the result with the ending MPG 10 3 Enter the program source code in a FORTH screen if mass storage is available Notice that blank lines enter lt SPACE gt followed by lt RETURN gt aid in source code readability MPG PROGRAM CONST VARIABLES 103 CONSTANT K O VARIABLE OLD MPG MPG 10 DISPLAY MPG S D t4 1 DIG 46 HOLD DEC PT HS 4 FINISH IT CR TYPE MPG The test of MPG puts a few numbers on the stack before the test number 456 and then execute MPG along with S to see that the Stack contents have not been altered 1 2 3 456 MPG 5 45 6 MPG 3 2 1 OK With MPG working correctly define TRUE MILES which uses as a scaling operator The constant k derived for each odometer and set of tires separately is multiplied by the miles traveled M OLD and then divided by 100 The decision point
84. These lower level words in turn are made up of other still lower level words which more precisely define the task accomplished by the word Finally you will arrive at a level which uses mostly regular FORTH words and is the most fundamental level not particularly obvious to anyone but the system programmer and then only when coding the word and for a short time afterwards Comments are necessary to understanding the operation of words What may be perfectly clear to you today will not be next month or to another equally qualified programmer at any time Comment in simple statements using the appropriate FORTH word names adjacently where you can Be a bit more detailed than you think necessary when you write them since they will be a bit too obscure later if you don t However comments are not tutorials to the novice or non programmer Too much verbiage obscures the program flow in a sea of text Commentary documentation that must speak to the non programmer should be written elsewhere in a companion document Comments given at the start of a FORTH word should include a simple statement about what the word takes from and leaves on the stack 10 2 EXAMPLE PROGRAM To illustrate the style and comment forms described above look at the many examples elsewhere in this manual and you will see the top down approach in use and reasonable comments that can be included on a printer This section t
85. Transmission XMTR Data Reg Empty XMTR Under Run Serial Communications Status Register Figure 9 2 Register Bit Assignments Continued 9 5 The direction of the page zero simplifies There are no direction registers associated with the 1 0 ports I O handling The I O addresses are shown in Table 9 2 Table 9 2 I O Port Addresses PA R65F11 and R65F12 R65F12 Only Bit Position Register Port REGISTERS Mode Control MCR Interrupt Enable IER Interrupt Flag IFR o O m Serial Communication Control SCCR Serial Communication Status SCSR PORTS PA Latch 1 1 1 1 k METS 4 PB Latch 1 E a i du 1 31 1 Figure 9 3 RES Initialization of 1 0 Ports and Registers I O lines are controlled by 8 bit port registers located in which register bits This can HEX FF PA C FF PB Inputs for Ports A and B are enabled by storing logic 1 s into all 1 0 port be accomplished by entering C Since the two ports Port A and Port B are adjacent in the memory map FFFF PA accomplishes the same thing A low input 0 8V signal causes a logic 0 to be read when the contents of the port is fetched A high input gt 2 0V causes a logic 1 to be read A reset forces all I O port registers to logic 1 s thus initially treating all I O lines as inputs The status of the input lines can be read at any time i e PB CQ Note
86. User variable containing current offset within input buffer A 4 INPUT OUTPUT BL H m UJ E DUMP o NULL END ET D D Continued Sed ARE ada oe addr addrl addr2 OUTPUT FORMATTI NUMBER S gt HOLD HLD TRAIL NG COUNT DPL A EM RS PENA uei n d ld Quse y addr I 2 Ial addr u addr nl addr n2 line SCR addrl addr 1 n n fie deus d fie addr ldwidth ldwidth Put a SPACE character ASC 20 on the stack Maximum number of characters line Terminal Input Buffer start addr Input text from terminal Print name given name field address NFA Dump n bytes starting at addr in ASC format in one semicolon record Dump bytes from addrl to addr2 in ASC format in as many semicolon records as required Also send closing record Executed at end of each input or screen line Not used by user Convert string at address to double precision number Start output string Convert next digit of double precision number and add character to output string Convert all significant digits of double precision number to output string Insert sign of n into output string Terminate output string ready for TYPE
87. W to the machine code for the definition 7 8 UP User Pointer containing the address of the base of the user area N A utility area in z page from N 1 thru N 7 7 5 2 CPU Registers When FORTH execution leaves NEXT to execute a CODE definition the following conventions apply a The Y register is zero It may be freely used ope The X register defines the low byte of the bottom data stack item relative to machine address 0000 X must point to the correct item upon returning to FORTH Gi The CPU stack pointer S points one byte below the low byte of the bottom item in the Return Stack Executing PLA will pull this byte to the accumulator d The accumulator may be freely used e The CPU is in the binary i e not decimal mode and must be returned in the binary mode with a CLD prior to return as needed 7 5 3 XSAV GI XSAVE is a byte buffer in z page for temporary storage of the X register Typical usage with a call to a previously defined code word USER which will change X is CODE DEMO XSAVE STX USER JSR XSAVE LDX NEXT JMP END CODE GI 7 5 4 N Area When absolute memory registers are required use the N Area in Page Zero These registers may be used to store pointers for indexed indirect addressing or to store temporary values The assembler word N returns the base address 0051 The N area spans 9 bytes from N 1 t
88. addr PD addr PC addr PB addr PA addr NMIVEC addr ROVEC addr NTVEC addr INTFLG addr SECURITY CSP o COMP CSP ERROR EXEC PAIRS STACK B CSP ABORT m List the first lines of all screens nl thru 23 Begin comment terminate by right parentheses on same line Alter parameter field pointer address to code field address Clear Return Stack and return to terminal Returns addr of Serial Channel Data Register Returns addr of Serial Channel Status Register Returns addr of Serial Channel Control Register Returns addr of Mode Control Register Returns addr of Interrupt Enable Register Returns addr of Interrupt Flag Register Returns addr of Port G Returns addr of Port F Returns addr of Port E Returns addr of Port D Returns addr of Port C Returns addr of Port B Returns addr of Port A Returns addr of low level Non Maskable Interrupt NMI vector Returns addr low level Interrupt Request IRQ vector Returns addr high level FORTH interrupt vector Returns addr of high level FORTH interrupt flag Store stack position into check stack pointer Error if not compiling Check stack position Outputs error message Not executing error Conditional not paired error Stack out of bounds error Use
89. an unsigned single precision remainder second on stack and an unsigned double precision quotient top of stack Examine with 54000 5000 M MOD D RETURN 10 4000 5 2 7 Scaling Suppose you are working with 16 bit integers and want to multiply one by a Scaling factor such as the sine of 45 degrees Since we are using only integers this sine value 0 7071 could be represented as multiplied by 10000 i e 7071 We want to multiply our number by 7071 and divide it by 10000 the problem is that the intermediate product is too large to represent as 16 bits so FORTH provides an operation times divide which multiplies the third term on the stack by the second item and then divides the result by the top of stack item while keeping a 32 bit intermediate product This is illustrated by 12345 7071 10000 RETURN 8729 Another operation MOD times divide mod performs the same operation but also returns the remainder as the second number on the stack Repeat the last example but also print the remainder 12345 7071 10000 MOD RETURN 8729 1495 5 3 OUTPUT FORMATTING The numeric output commands described in Section 4 11 1 are enough for most programs However some applications need special formats such as decimal points and dollar signs with printed numbers or colons within numbers to indicate degrees minutes and seconds FORTH includes special output op
90. and three nested loops do the work 0 VARIABLE COUNTS 1 ALLOT CODE COUNT DOWN O LDA COUNTS STA COUNTS 1 STA U B COUNTS 2 STA N EGIN OUNTS DEC UNTIL COUNTS 1 DEC 0 UNTIL COUNTS 2 DEC 0 UNTIL NEXT JMP END CODE Goawag Execute the counter COUNT DOWN lt RETURN gt OK About 21 min The breakdown of the machine code is 041F 00 00 00 COUNTS Variable 0422 8A Name Field Start 0423 43 4F 55 4E 54 2D 44 4F 57 CE COUNT DOWN Name 042C 11 04 Link Field 0411 042E 32 04 PFAPTR 0432 0430 32 04 Code field 0432 0432 A9 00 LDA 4500 Parameter Field 0434 8D 1F 04 STA 041F 0437 8D 20 04 STA 0420 043A 8D 21 04 STA 0421 043D CE 1F 04 DE 041F 0440 DO FB BNE 043D 0442 CE 20 04 DEC 0420 0445 DO F6 BNE 043D 0447 CE 21 04 DEC 0421 044A DO F1 BNE 043D 044C 4C 28 F4 JMP F428 7 7 When concluding a CODI RETURN OF CONTROL E definition several common stack manipulations are often needed These functions are already in the nucleus so we may share their use just by knowing their return points Each of these words ultimately returns control to NEXT POP Remove one 16 bit stack value POPTWO Remove two 16 bit stack values PUSH Push two bytes
91. are contained in the ROM including 16 and 32 bit mathematical logical and stack manipulation plus memory and input output operators The RSC FORTH Operating System allows an external user program written in RSC FORTH or Assembly Language to be executed from external EPROM or development of such a program under the control of the R65FR1 RSC FORTH Development ROM 2 1 2 Configuring an R65F11 R65F12 Based System There are several ways to configure an R65F11 or R65F12 based system A minimum system includes the R65F11 or R65F12 microcomputer a crystal application program in PROM ROM and application input output interface Such a system can be expanded in memory up to the 16K address limit of the R65F11 R65F12 The R65F1 Development ROM may be included in any RSC FORTH system by providing proper decoding logic There are two basic configurations of RSC FORTH based systems a Using an R65F11 An external addressing space of 16K bytes is possible with the use of an eight bit latch The R65FR1 at address 2000 3FFF may be used as a development ROM Two I O Ports A B are available to the user b Using an R65F12 Five I O ports A B E F and G are available to the user All other comments are the same as for the R65F11 Additional ROM RAM and I O devices can be added to the external memory map as desired Figure 2 1 shows a RSC FORTH memory map Figure
92. bytes in code most unique feature of the RSC FORTH Kernel is the built in floppy lows a RSC FORTH Microcomputer to control up to 1 2 disk drives with 2 4 megabytes of on line The words inside the kernel plocks ed from are label X non with most FORTH systems ero to n lock in memory either from or to the f where n number of disks Mass Storage Words The higher level that R W the disk hand storage words of RSC FORTH contained in the R65FR1 Development ROM kernel UR W H 8 internally three n used t Boolean into me umbers The lowest of he second is the block value telling whether mory location 800 an EX E 00 20 1 R W has the same effect as 800 20 1 DISK DISK initiates the correct sequence of lower level disk handling words SELECT SE is a system variable in t E n has LOAD R W to read or write entry of EK UR W BLOCK ar designed to read or write a Loppy disk drive The higher level words used for mass storage all eventually refer to calls the appropriate disk and has no function other than to pass control from t ler via a vector contained in Suc handler primitives BUFF all mass storage is designated in groups Each block on the disk has an identifying number number of blocks per side x a word word is r
93. change CONTEXT to point to its last word e g VOCABULARY NEW To add words to NEW now type NEW DEFINITIONS T because DEFINITIONS sets CURRENT equal to CONTEXT allowing new words to be added to the NEW vocabulary Now add a new word MYWORD NEW VOC and type VLIST and get 42C MYWORD 336 417 40B TASK 3844 ADMP 3805 DUMP 37CF FORMAT 367E FMTRK 3674 BANKEXECUTE 3664 BANKEEC 3657 BANKC OK SPACE bar pressed here Now type FORTH this will set CONTEXT back to the FORTH vocabulary and MYWORD will not show up on a VLIST but it will execute Now type FORTH DEFINITIONS changing both CURRENT and CONTEXT to the FORTH Dictionary Now MYWORD will not show up in VLIST and will not execute To use MYWORD one needs only to link the NEW vocabulary to FORTH by typing NEW It is generally recommended that use of sub vocabularies be avoided and all user defined vocabularies be created in FORTH This is for compatibility with many other FORTH systems which only allow one level of vocabulary nesting Vocabularies are optional needed for advanced users only Most programs only use the default FORTH vocabulary and the programmers do not even need to know that vocabularies exist 5 7 IMMEDIATE WORDS Most FORTH words will be compiled not executed when they are
94. clear counts to zero we decrement it and it becomes FF This way we loop 256 times before finally exiting when we decrement to zero b A 16 Bit Counter This counter is similar to the 8 bit one except that COUNTS is the right size to begin with therefore ALLOT is unnecessary We initialize two bytes to zero to start with We use two nested loops to do the decrementing The assembly code is 0 VARIABLE COUNTS CODE COUNT DOWN 0 LDA COUNTS STA COUNTS 1 STA B N BEGIN COUNTS DEC 0 UNTIL UN D CO NEXT END Execute the counter COUNT DOWN lt RETURN gt OK The machine code is 041E 00 00 COUNTS Variable 0420 8A Name Field Start 0421 43 4F 55 4E 54 2D 44 4F 57 CE COUNT DOWN Name 042B 11 04 Link Field 0411 042D 31 04 PFAPTR 0431 042F 31 04 Code Field 0431 0431 A9 00 LDA 00 Parameter Field 0432 8D 1E 04 STA 041E 0435 8D 1F 04 STA 041F 0438 CE 1E 04 DEC 041E 043B DO FB BNE 0432 043D CE 1F 04 DEC 041F 0440 DO F6 BNE 0432 0442 4C 28 F4 JMP F428 Cx A 24 Bit Counter The value of indenting the loops for visual clarity is more obvious here than in the previous example This example uses a three byte counter and so one more byte of dictionary space is allotted
95. displaying data in that base FORTH will stay in the selected base until the base is changed or until FORTH is reinitialized to DECIMAL Note that DECIMAL and HEX affect the input and output data representation and not internal data handling Reinitialize FORTH and put the following numbers on the stack and print them using different combinations of Press RETURN after the word COLD RETURN DEC Initializes RSC FORTH VI 5 16 16 OK 16 HEX 10 OK 10 DECIMAL 16 OK 255 255 OK 255 HEX FF OK DECIMAL 32767 32767 OK 32767 HEX 7FFF OK DECIMAL 32768 32768 OK 32768 HEX 8000 OK IMAL DECIMAL and HEX in each of the following examples Note that DECIMAL numbers 1 to 32768 entered on the stack will be displayed in HEX in 2 s complement form with a leading minus sign We will examine other number bases later see Section 4 11 3 4 2 STACK MANIPULATION Since most FORTH words use the stack to hold input or output numbers let s explore some FORTH words that are used to rearrange or copy numbers near the top of the stack While these functions are sometimes necessary you should avoid using them where possible FORTH code is more readable when less stack manipulation is used Common stack manipulation words are discussed here however to give you additional experience in working with the stack before proceeding into other FORTH word descriptions
96. element of ARRAY X Y Oth element of ARRAY Y Y 9th element of ARRAY Y Oso to return the addresses of the first 0th and last elements of X and Y We can then use the arrays to store and fetch data using and Note that there are 50 elements in ARRAY X numbered from 0 to 49 and similarly there are 10 elements in ARRAY Y numbered from 0 to 9 How do we define ARRAY to do this We could use ARRAY BUILDS 2 ALLOT DOES SWAP 2 How does this definition work he BUILDS part tells what happens at compile time The argument on top of he stack to ARRAY 50 or 10 in the above example is multiplied by two and LLOT leaves that many bytes of space in the dictionary Note that when or Y or any other array is being defined the appropriate number of bytes ust be allotted for it S wv mcd The DOES part tells what happens when X or Y is executed At execution of OX 49 X etc DOES automatically causes the system to place the address of where the array begins on top of the stack any arguments 0 49 or 9 in hese examples are below that address The SWAP brings the array index to the top of the stack where it is multiplied by two to get its byte offset from the beginning of the array This offset is then added to the address of the array to get the desired address of the particular element ct To see how the allocation works after entering the definition of A
97. example FORGET TASK OK TASK OK EX OK 04 10 DUMP 404 84 54 41 53 CB 3D 38 F 4 74 F8 17 F7 4 44 55 SSH e OK Now look at its component parts 404 84 8 MSB 1 start of a word 4 Number of characters in TASK 405 54 41 53 CB ASC characters for TASK with MSB of last character set to 1 409 3D 38 Link address of 383D links to ADMP word in the RSC FORTH Development ROM 40B OF 04 Parameter Field Pointer address links to Parameter Field location 40D 74 F8 Code address of F874 indicates colon definition 40F 17 F7 Parameter address of F717 indicates the end of a colon definition isep got 5213 For both CONSTANT and VARIABLE words the parameter field is two bytes long and contains the value of the constant or variable For USER words the parameter field is one byte long and contains the offset into the user area for the USER variable 5 5 2 Handling FORTH Word Addresses There are five FORTH words concerned with finding the address of the various word fields They are tick PFAPTR Parameter Field Pointer Address CFA Code Field Address LFA Link Field Address NFA Name Field Address ae c leaves the parameter field pointer address PFAPTR of the word following it on the stack b NFA converts the parameter field pointer address on the Stack into the name fi
98. for CENTS GAL tells if the price for a gallon or liter is 1 00 and should be correct for a while yet The adjustment for liter prices is 3785 1000 which results in cents per gallon equivalent Now enter the rest of the code definitions IRUE MILES ODOMETER ADJUST MILEAGE OLD OLD 4 OVER OLD NEW 4 MILES K CORRECTION 100 ADJUST CENTS GAL PRICE CONVERT PRICE DUP FOR COMPARE 1000 lt 1 00 IF CENTS LITER 3785 100 THEN 10 4 MPG ODO PRICE AMT DISPLAY MPG ROT GET ODOMETER TRUE MILES ROT GET PRICE CENTS GAL ROT GET AMOUNT COMPUTE MPG MPG amp PRINT RETURN If any errors occur during compilation check the source code for entry errors Compile each word separately if needed to verify proper coding by bracketing each word with parenthesis before the word before the and after the word after the as comments d Program Final Testing e The testing of MPG involves entering some known values into it and observing the results Don t forget to set the OLD value for the odometer reading first as shown below Then enter test values on the stack for the current odometer reading the price and the miles trave
99. form would be ENDIF COMPILE THEN MMEDIATE This defines ENDIF to work the same as THEN 5 8 CREATING YOUR OWN DATA OPERATION TYPES The RSC FORTH system includes several defining words that is words which create new words The most important of those are the colon CODE CONSTANT VARIABLE S USER and VOCABULARY The defining words C CON and CASE are unique to RSC FORTH and are discussed separately in Section 6 You may want to create new defining words In general each new defining word creates a new type of data structure of operation Examples might be ARRAY MATRIX CUSTOMERRECORD and VIRTUAL ARRAY FORTH assemblers use similar structures for classes of instructions such as one and two byte addresses New data or operation types are usually created by the pair words BUILDS and DOES these words are always used together The word CODE is an alternative way to create new data structures they run faster but require use of the assembler s Section 6 9 For example suppose we want a word to create arrays of 2 byte 16 bit memory locations numbered from zero We want to say e g 50 ARRAY X 10 ARRAY Y to create arrays X and Y1 with 50 and 10 elements respectively Then we want to use these arrays as X Oth element of ARRAY X 9 X 49th
100. if nl greater than n2 nln2 f True if top two numbers are equal 0 ASES True if top number negative 0 2 TS ELO True if top number zero i e reverses truth value U lt GALb u2o f True if ul less than u2 NOT Erre EN Reverse Boolean value same as 0 A 5 CONTROL STRUCTURES DO LOOP end 1 start Set up loop given index loop range DO ass n end 1 start Like DO LOOP but LOOP n loop add stack value instead of always 1 to index I index Place current index value on stack LEAVE Terminate loop at next LOOP or LOOP BEGIN BEGIN UNTIL Loop back to BEGIN until UNTIL true at UNTIL BEGIN BEGIN f Loop while true at WHILE WHILE REPEAT WHILE REPEAT loops REPEAT unconditionally to BEGIN BEGIN Unconditional loop AGAIN TE 24s THEN ifs GE If top of stack true execute A 3 A 5 CONTROL STRUCTURES E LSE i Ha A EN ECUTE CMOVE FILL ERASE BLANKS TOGGLE EEC BANKC BANKC BANKEE a ee ee eat CR SPACI SPACI LH GI DUMP TYPE TERM EXPECT WORD NAL WEM um LUE ges A A INPUT OUTPUT Ed Toss addr n addr n n addr addr b b addr addr Continue
101. into the data stack Must be followed by a multi mode op code mnemonic addr 1 cc assembly time CONTROL run time anti Occurs in a CODE definition in the form BEGIN des CC UNTIL At assembly time UNTIL assembles a conditional relative branch to addr based on the condition code cc The number 1 is used for error checking At run time UNTIL controls the conditional branching back to BEGIN If the processor status bit specified by cc is false execution returns to BEGIN otherwise execution continues ahead WORD UP VS STACK NOTATION DEFINITION GROUP addr assembly time REGISTER user pointer Used in a CODE definition in the form UP LDA or UP Y STA A constant which leaves the address of the pointer to the base of the user area The instructions HEX 12 LDY UP Y LDA will load the low byte of the sixth user variable DP cc assembly time CONDITION overflow set Specifies that the immediately following conditional will branch based on the processor status overflow flag being on V 1 The flag cc is left at assembly time there is no run time effect on the stack addr assembly time REGISTER Used in a CODE definition in the form W 1 STA or W1 JMP or W Y ADC At assembly time constan
102. minimum external circuitry excluding chip decode required to connect the R65F11 R65F12 to the 1793 and support circuits In addition the RSC FORTH operating system provides the complementary software interface Figure M 2 shows the memory map of words bytes assigned to transfer data and command status between the R65F11 R65F12 and the 1793 FDC device The 1793 Data 1793 Sector 1793 Track and 1793 Status Command bytes all conform to the standard 1793 interface definitions The bit definitions for the DRIVE STAT read R W 1 and DRIVE CTL write R W 0 are shown in Figure M 3 READ DATA WRITE DATA i mm SIDE SELECT D1 DRIVE SELECT 0 D2 D3 DRIVE SELECT 2 CONTROL REGISTER CHIP SELECT RESET Figure M 1 R65F11 R65F12 Floppy Disk Controller Interface M 2 SOLFF NOT USED 0107 0106 DRIVE STAT CTL 0105 0104 NOT USED 0103 1793 DATA 0102 1793 SECTOR 0010 1793 TRACK 0100 1793 STATUS CMD Figure M 2 Floppy Disk Controller Memory Map INTRQ FROM 1793 DENSITY O Double 1 Single INTRQ DRQ FROM 1793 NOT USED MOTOR ON STATUS MOTOR ON CONTROL O ON 0 OFF 1 OFF 1 ON NOT USED DRIVE SELECT 3 NOT USED DRIVE SELECT 2 NOT USED DRIVE SELECT 1 NOT USED DRIVE SELECT O NOT USED SIDE SELECT 0 Side 0 l Side 1 Figure M 3 DRIVE STAT DRIVE CTL Bit Definitions M 3 This page is intentionally left blank APPENDIX
103. n itself and places it on top 1 PICK is the same as DUP and 2 PICK is the same as OVER Put several numbers on the stack and check them 40 50 60 70 80 S RETURN 80 70 60 50 40 111 222 333 OK Now pick the 4th item i e 50 and look at the results 4 PICK S RETURN 4 3 MEMORY OPERATIONS Several FORTH words move data between the stack and memory or from memory to memory 4 3 1 16 Bit Store and Fetch The FORTH word pronounced store takes an address from the top of the stack and the 16 bit value beneath it and stores the value into the address and address 1 A corresponding word pronounced fetch takes an address from the top of the stack fetches the 16 bit data from that address and address 1 and replaces the address on top of the stack with the data from memory Both the address and the data are specified in the current number base Initialize FORTH and try COLD RSC FORTH V1 6 HEX OK 30FF 200 OK 200 CR 30FF OK which stores 30FF into addresses 200 and 201 with fetches the contents of addresses 200 and 201 with and displays it with Try DECIMAL 16000 HEX 200 OK to store a decimal number in an address entered in hexadecimal Now display the data in decimal by 200 DECIMAL CR 16000 OK which fetches the contents of addresses 200 and 201 and stores it o
104. of next buffer Variable containing address of latest buffer Leaves address of first block buffer Top of memory User variable block offset to mass storage Sets LIMIT to n FIRST to n COC User variable currently selected disk User variable four bytes each byte holds current track for each of four disk drives User variable blocks per side per drive Accesses disk read if b 1 write if b 0 block number n at addr Selects disk drive n n 0 3 Seeks track n on selected drive Reads multiple 4 disk sectors starting at sector 4n 1 of selected disk urrent track to addr and leaves he disk error byte Writes multiple 4 disk sectors starting at sector 4n 1 of selected disk current track to addr and leaves the disk error byte Sets current tracks in CYLINDER to SFF s which forces recalibration on next disk access Format nl tracks on disk number n2 Format track nl on side n2 of the selected disk Puts text following into line n of current screen in buffer A 9 ta A 14 MASS STORAGE NDEX nl n2 Continued A 15 MISCELLANEOUS AND SYSTEM comment CFA pfaptr cfa QUIT SCDR addr SCSR addr SCCR addr MCR addr ER addr TFR addr PG addr PF addr PE
105. other programmers As new words are defined they are added to the FORTH vocabulary described in more detail in Section 5 6 These definitions are normally stored in RAM starting at address 0404 and build upward in memory They can also be stored in PROM ROM in normal or headerless target compiled format as described in Section 11 The FORTH word VLIST allows you to check what words have been added to the FORTH vocabulary 4 4 1 Colon Definition Suppose we want an operation to take the number on top of the stack multiply it by 5 and print the result Let s pick the name TEST OP We could define it simply as TEST OP 5 RETURN OK Later we will rewrite this definition using indentation and commenting conventions for more readable code Enter the colon definition as follows a Start the definition with a colon which tells FORTH to look ahead in the input stream for the word name Follow the colon with a space b Enter the word name up to 31 characters The FORTH word here is TEST OP c Enter the definition of the word TEST OP does the following Puts 5 on the stack 2 Multiplies the top two numbers i e the number on top of the S T tack when TEST OP is executed by the 5 put on the stack by EST OP 4 17 3 Prints the result i e the top number on the stack d End the definition with a semi colon
106. output single precision and double precision numbers left justified and right justified The word R prints a 16 bit number right justified in a field of a given width It takes two arguments the number and the desired field width the latter is on top of the stack For example 4734 CR 26 R CR 4734 OK prints 4734 right justified 26 columns Note the use of CR to cause OK to print on the following line Later in Section 5 2 2 you will see that the corresponding double precision 32 bit output word D prints a double precision signed number left justified while D R prints a double precision signed number right justified 4 12 2 Output Spaces with SPACE and SPACES The word SPACE outputs one space and SPACES takes one argument from the Stack and outputs that number of spaces such as CR TEXT1 4 SPACES TEXT2 CR TEXT1 TEXT2 OK 4 12 3 Output a Character with EMIT Use the word EMIT to take the top stack number as an ASC value and output it For example DECIMAL 65 EMIT outputs A to the terminal GI Use EMIT in conjunction with the input word KEY see Section 4 13 1 to display an entered character Try it with KEY lt RETURN gt lt input character gt OK EMIT Entered character OK Note that the input character from the keyboard is not output
107. quickly Each module should be short in the programming style preferred by most FORTH users so that all possible paths of control can be tested easily If correct results are not obtained it is possible to step through the definition by executing each component word individually checking the stack whenever desired RSC FORTH has a special word S which non destructively prints the stack contents to help in this kind of debugging Any unexpected results can be localized to a particular component word which in turn can then be examined in detail Because FORTH words work identically when compiled or when executed as commands the programmer can debug at either a batch or interactive operation mode Because FORTH is extensible words can be re defined to perform their original functions and in addition give special debug print outs or do run time error checks These redefinitions can be inserted into programs for testing and removed later nothing else in the program need be changed RSC FORTH also includes a memory dump and other words for examining or changing memory These commands can be compiled into programs or executed from the keyboard In contrast to most other operating systems all of these tools are part of the normal FORTH environment No special syntax or command language must be learned for debugging Each FORTH word is documented by a glossary see Appendix B which l
108. s Tes 5 6 2 CONTEXT and CURRENT Specify Vocabularies vus 5 6 3 Use LATEST and HERE to Check Directory 56 4 Application Libraries Lows 4 A S MR Su Jimmedrate WOrAS gy iama Go ies blows Me stessa LA M Lr Mis V dea Seals 5 8 Creating Your Own Data Operation Types 6 SPECIAL OPERATIONS G l System Constants pueri mee wo ie ue eU d etse esee EL prep ers 6 2 Defining Words i es ed ek RPG ds a 6 2 1 Creating Address Constants with C CON 6 2 2 Selecting Words with CASES 44 v ed bg Y 6 3 Target Compilation Dictionary Control 6 3 1 Headerless Code Generating 6 3 2 Target Compilation with H C eee 6 3 3 Codes Versus Heads Dictionary Words 6 3 4 Move a Definition from Codes to Heads with HWORD Z5 atus d far ox ad ferret ree cm af PURI Ier aue etie Pus 6 3 5 Preparing for Autostarb e o o e ers Ged DESK TInterftactHg wee a pna e aue Sad eae Se UTE dece 6 4 1 High Level Mass Storage Words 6 42 Disk System Variables sieaa ii wo wg wy Nu 6 5 Genera TU RIPE RES lle bg VIL Dee Lael ides 6x51 Formatting a DESK 219 d IRR Aedes 62532 Screen ModTficdtYOnD eects RR re 6 5 3 Dumping a Memory BLOCK i e 9 e emnes 6 5 4 Using EEC to Program a PROM 645 5 Bank SwitcohDlung Lt icu a at epee ce Ce ned m nera 6 5b 6 Specifying TOp oft Memory eii 1 V ii EA vi 6 6 6 6
109. that this returns the actual status of the input lines not the data stored in the I O port register Port outputs are control Lled by storing the desired I O line output states into the corresponding 1 0 port register bit positions A logic 1 forces a high output gt 2 4V while a logic 0 forces a low output 0 4V The settings of the Mode Control Register MCR and the Serial Channel Control Register SCCR determine whether Port A operates as a standard 8 bit bit independent I O port or serial I O lines counter I O lines or input data strobe for Port B latching Table 9 3 tabulates the control bit settings and usage of Port A In addition to their normal I O functions PAO and PA1 can detect positive going edges and PA2 and PA3 can detect negative going edges A proper transition on these pins will set a corresponding status bit in the IFR Port B can operate as an 8 bit bit independent I O port This port also has a useful function when used as an input port in that the input values can be latches at a particular point in time based on a hardware event If MCR bit 4 is set to a 1 reading Port B gives the value present the last time PAO was pulsed PAO is positive edge sensitive By using this feature the processor does not have to continuously polled for an event on Port B to know when to read Port B The value on Port B is
110. the address parameter field of the word s The new word is created in the CURRENT vocabulary addr SECURITY U Nego Leaves the address of a user variable temporarily storing the check stack pointer CSP position for compilation error checking addr VOCABULARY current Leaves the address of a user variabl e pointing to the vocabulary into which new word definitions are to be entered WORD CYLINDER D DABS DECIMAL STACK NOTATION DEFINITION GROUP ATTR addr MASS cylinder User variable four bytes long used as an array Each byte contains the track number of corresponding disk dl d2 d3 ARITHMETIC d plus Adds double precision numbers dl and d2 and leaves the double precision number sum d3 db dgc d2 ARITHMETIC Applies the sign of n to the double precision number dl and leaves it as double precision number d2 dE FORMAT d dot Displays a signed double precision number from a 32 bit two s complement value The high order 16 bits are most accessible on the stack Conversion is performed according to the current BAS A blank follows Ed dd gt FORMAT Displays a signed double precision number d right aligned in a field n characters wide d ud ARITHMETIC d abs Leaves the absolute value ud of a double number
111. the operation of 2 two NUMERIC The number two is placed on top of the stack n n 2 two plus fioe m 2 two minus Decrements n by two d A or nl n2 gt two drop Drops the top double ARITHMETIC Increments n by two according to the operation of ARITHMETIC according to the operation of STACK number on the stack WORD 2DUP STACK NOTATION DEFINITION GROUP ATTR do d d STACK or nl n2 nl n2 n1 n2 two dup Duplicates the top double number on the stack ZDR NUMERIC three The number three is placed on top of the stack 4 NUMERIC four The number four is placed on top of the stack DEFINING t colon A defining word used in the form name 5 Selects the CONTEXT vocabulary to be identical to CURRENT Creates a dictionary entry for name in CURRENT and sets the compile mode Words thus defined are called colon definitions The compilation addresses of subsequent words from the input stream which are not immediate words are stored into the dictionary to b xecuted when name is later executed MMEDIATE words are executed as encountered If a word is not found after a search of the CONTEXT and FORTH vocabularies conversion and compilation of a literal number is attempted with regard to the
112. the word that would be put in ULIMIT from step 1 accomplishes all the above tasks automatically Step 5 is necessary if a value other than zero is desired as FORTH adds this offset value to each block number requested via R W The utility of OFFSET is in setting it to the first block number in an extra mass storage device Then the block numbers of media inserted in that device will be the same to the user as when OFFSET is zero and the media is in the primary device This is important if there is more than one disk drive 12 3 Table 12 1 Buffer Variables Constants and Access Words pu ee o o Access Default Variable Word Value Description A A MM ee eT Holds the number of bytes of data in each block buffer The actual buffer size is four bytes larger than th s value This number is a constant in RSC FORTH and cannot be changed UB SCR Holds the number of block buffers per FORTH screen l This number is a constant in RSC FORTH and cannot be changed UFIRST Holds the location of the start of the data buffer ULIMIT Holds the location of the end of the data buffer plus one PREV Holds the address of the block buffer most recently referenced USE Holds the address of the block buffer to use next OFFSET Holds a value to be added to the block number given to BLOCK NOTES Variables without a special access word to fetch the value are treated like any other FORTH v
113. to the definition to be autostarted AUTOSTART requires only an address specifying where the autostart pattern is to be placed and the name of the routine to autostart For example if GO TO IT was the main routine of a dedicated application HEX 800 AUTOSTART GO TO IT puts A55A at address 800 followed by a pointer that identifies the location of the PFA of GO TO IT The value stored there is the equivalent of GO TO IT Once the RAM image is established the PROM can be made by using ADMP to transfer the RAM image to a PROM programmer or using the EEC functions described in Section 6 In summary the steps to enter a program into EPROM is as follows a Write enter test and debug the application program on the development system Save the source code b Enter COLD to initialize the RSC FORTH System c Enter FORGET TASK to remove the linkage to TASK d If moving the address of the target code area enter XXXX ALLOT or YYYY DP where XXXX number of bytes to move the starting address from 0400 YYYY actual starting address to be used NOTES XXXX must be multiple of 1024 400 YYYY should be four bytes from a 1K boundary i e 804 C04 1004 etc to leave room for a preceding autostart pattern Watch the number base when entering e If using target compiled code enter Zaun BO where ZZZZ the address to put the dictionary head
114. used inside a colon definition Immediate words are the exception They ar xecuted even at compile time The words used for conditional branching and looping e g IF THEN DO LOOP BEGIN etc are all immediate words They execute at compile time in order to handle forward or backward branch references various error checks and other functions Some of these words such as DO and LOOP place special run time words not used directly by the programmer into the object code But some e g BEGIN place nothing at all in the object code To define a new immediate word use MMEDIATE after its definition i e after the semicolon This causes the last word defined to be immediate On rare occasions the programmer must force compilation of an immediate word To do this use COMPILE the brackets are part of the name before the immediat word to be compiled For example suppose you want to run source code written for an older version of FORTH which used the name ENDIF for THEN RSC FORTH supports both of these words You don t want to go through the code and make all the changes It would be wrong to define ENDIF by ENDIF THEN IMMEDIATE because the THEN would try to compute a conditional branch and cause an error message because there is no corresponding IF The correct
115. 099F40AD6 ri works only with R65F11 and R65F12 2 The word th PROM programmers for large in respect to and le to use the R65F11 or R65Fl accomplishes this EEC y ar xpensiv 12 to for a single byte at a time by manipulating the address and data bus to be stable for the period required for programming EEROM can be programmed directly in a socket without extra To program PROMs that require a larger programming voltage l amount of external hardware must be added to apply The 2764 variety PROMs have a separate minimal during programming easily more fami handled elaborate circuitry to mul ly is very difficult to program because the programming pulse is positive The 2732 famil In fact ly has a combination VPP and ltiplex the normal O programming a Rockwell 5213 2816 voltages VPP than 4 5V a VPP to the device VPP pin and OE going and not readily generated with R W alone Three para the data byte to be put in PROM programmed hold the b into 5213 2816 E device Output Enable OE located at address 0800 meters must be supplied to us stable while the PROM programs EROM is in a socket previously set up and tested for a Chip select is generated by decoding the address bus when is the logical NAND of 02 and R W In order to progr
116. 2 1 Single Mode Op Codes The R6500 single mode op codes ar BRK CLC CLD CLI CLV DEX DEY INX INY NOP PHA PHP PLA PLP RTI RTS SEC SED SEI TAX TAY TSX TXS TXA TYA When any of these op codes ar xecuted the corresponding machine code byte is assembled into the dictionary 7 2 2 Multi Mode Op Codes The multi mode op codes ar ADC AND CMP EOR LDA ORA SBC STA ASL DEC INC LSR ROL ROR STX CPX CPY LDX LDY STY JSR JMP BIT RMB SMB These op codes take an operand which must already be on the stack An address mode may also be specified If none is given the op code uses z page when appropriate or absolute addressing 7 3 ADDRESSING MODES The addressing modes are specified by FORTH Addressing Address Word Mode A accumulator none immediate 8 bits only 1X indexed X z page or absolute s indexed Y z page or absolute X indexed indirect X z page only Y indirect indexed Y z page only indirect absolute only none memory z page or absolute Here are examples of FORTH vs conventional assembler Note that the operand comes first usually followed by any addressing mode modifier and then the op code mnemonic This makes best use of the stack at assembly time Also each assembler word is set off by blanks as is required for all FORTH source text
117. 2 2 shows a typical maximum electrical hook up for an R65F11 system with and R65FR1 Development ROM and RS 232C serial interface for connection to a CRT keyboard terminal Wiring for an R65F12 system would be almost identical 2 2 RSC FORTH SOFTWARE 2 2 1 Operating System Much of the philosophy needed to build a RSC FORTH microcomputer system can be understood by looking at the RSC FORTH operating system Many cost effective eight bit memory devices are available to the system designer today These ROMs RAMs EPROMs and EEROMs usually come in multiples of 1K byte increments The most popular are the 2K byte versions such as the 2016 6116 and similar RAM devices and the 2716 type EPROMs The RSC FORTH Operating System is designed to work with these memory products The purpose of an operating system is to initiate operation in an orderly manner during power on or reset the loading and starting of user functions and allocation of system resources The RSC FORTH Operating System provides these and many other services Since the RSC FORTH system is designed to serve in a dedicated application the operating system s unique power up procedures are most interesting Upon reset the reset vector in the kernel ROM directs processor execution to a section of machine code in the FORTH word COLD This initializes the microcomputer for operation Register values are established and interrupt Sou
118. 46 is the decimal point S 36 HOLD SIGN 4 36 is the dollar Sign TYPE SPACE The following examples show that the leading zeros are handled properly 555 D RETURN 5 55 5 D RETURN 0 05 If three places after the decimal point were desired one additional would be necessary before the 46 Let s define another word that uses DS to print multiple numbers PRINT DS CR 0 DO DS CR LOOP Now put four numbers on the stack and print them 123 45678 3456 23456 4 PRINT DS Print four numbers 234 56 34 56 456 78 S23 The following word prints a mixed number when the integer double precision number is on top of the stack and the position of the decimal point is held in the user variable DPL HEX XN SWAP OVER DABS Set form for sign and conversion lt DPL DUP Convert digits to right of IF 0 DO LOOP THEN decimal point 2E HOLD S SIGN gt Convert decimal point and remainder of digits TYPE SPACE Print results DECIMAL Verify proper conversion with an example such as 34 786 XN RETURN 34 786 5 4 STRINGS FORTH does not have a standardized package of string handling operators but it does have primitive operations from which string routines can be built For many applications the primitives themselves ar nough A series of string handling functions that ca
119. 5D 05D 0C1 0C2 0FF 100 101 102 103 106 No PAGE Cold Start Hex Bytes Value p H i PNNNNN DN O Or RFPND N N OO 100 60 APPENDIX F N Warm Start Hex Value ERO and ONE MEMORY MAP Parameter Name Parameter Description Internal ports Internal registers B Reserved ROVEC NMIVEC UKEY UEMIT UP INTFLG w 1 W IP N 1 N XSAVE NTVEC High level interrupt vector TOS Last free memory in data stack Parameter data stack Return stack Floppy Disk Status Command Register Floppy Disk Track Register Floppy Disk Sector Register Floppy Disk Data Register Floppy Disk Control Register This page is intentionally left blank APPENDIX G USER VARIABLES RAM MAP Cold Warm Start Start Hex No Hex Hex Parameter Address Bytes Value Value Name Parameter Description 300 301 2 80 03 80 03 TIB Terminal Input Buffer address 302 303 2 FF 00 FF 00 RO Return Stack base address 304 305 2 C2 00 C2 00 S0 Parameter Stack base address 306 307 2 50 00 ct ue UC L No of characters line 308 309 2 TE 03 ye E UPAD Location of PAD in memory 30A 30B 2 DISK 15 UR W CFA of UR W orphan word 30C 30D 2 10 00 BASE Current 1 0 base number 30E 30F 2 EM EA CLD WRM Cold warm reset flag 3102311 2 mue ELM IN Byte o
120. 651N49 R65F11 and R65F12 FORTH Based Order No 2146 Microcomputer Product Description 29651N59 RSC FORTH Reference Card Order No 2156 29651N65 Application Note A Low cost Order No 2162 Development Module for the R65F11 FORTH Microcomputer This page is intentionally left blank FUNCTIONAL DESCRIPTION The RSC FORTH system integrates a complete ROM based FORTH system consisting of microprocessor memory and peripheral hardware elements and RSC FORTH software into a single chip microcomputer for runtime applications and a two chip set for application software development The RSC FORTH software includes a Software Kernel comprised of an RSC FORTH Operating System and runtime portions of the RSC FORTH language which is masked into ROM in the one chip microcomputer Two versions of this microcomputer are available the R65F11 and R65F12 Each version has the same Software Kernel but different input output capabilities The other portions of the RSC FORTH software not required at runtime are provided in a separate and supporting R65FR1 Development ROM for use during application program development The hardware elements of the microcomputer and the features of the operating system are presented first so the interaction with the runtime and development portions of the RSC FORTH language can be fully understood 2 1 RSC FORTH HARDWARE 2 1 1 R65F11 and R65F12 Micro
121. 7 608 609 command can be useful The that the codes ar It is evident her and the heads at 600 being generated at the 400 memory space By this example and comparison of the two memory sections it should be clear that target compilation can save a great deal of space in codes area 6 3 3 Codes Versus Heads Dictionary Words HEADERLESS ALLOT puts a 16 bit value in th In the target compile mode space in the codes area while Similarly j contains a one reserves bytes in the heads dictionary codes area whereas ALLOT provides free puts a 16 bit value in the heads dictionary Any of these words modify the system variables at the addresses of DP adjacent in memory and DP DP 32A RETURN OK DP 32C RETURN OK The words ending in simply use DP plus two if The physical addresses of DP and DP are HEADERLESS is non zero 6 3 4 Move a Definition from Codes to Heads with HWORD A useful dictionary control word HWORD picks up a definition from the target codes area and places it in line in the heads dictionary HWORD works on the last definition entered Try entering HWORD now Since the last entry was TASK the code for TASK will no longer be in the codes area This can be verified by checking its CFA TASK CFA RETURN 609 OK HWORD is often useful for moving the code for a test word out of the target area
122. 89 4 30 CR D R 12894 Define a word to print multiple double precision numbers right justified 15 columns PRINT RIGHT N 0 DO CR 30 D R LOOP CR Enter the data on the stack and print it with PRINT RIGHT Place the numbers and the number of items on the stack before calling PRINT RIGHT 456 23145 879 12894 4 PRINT RIGHT 12894 879 23145 456 5 2 3 Other 32 Bit FORTH Operators There are several other double precision FORTH words which are analogous to the single precision operations Double precision add D d plus operates in the same manner as except it uses the top two double precision numbers on the stack as inputs and leaves one double precision number e g 3456 6576 D D RETURN 10032 DABS d abs returns the absolute value of a double precision number similar to the single precision word ABS 76543 DABS D RETURN 76543 DNEGATE d negate changes the sign of the double precision number on the Stack allowing subtraction 768945 DNEGATE D RETURN 768945 The word S gt D s to d converts a single precision number on the top of the stack to double precision number 6758 DUP CR 6758 S D CR D 6758 The operation D d plus minus applies the sign of the single precision number on top of the stack to the double precision number beneat
123. A digit indicates number of memory addresses used if other than one E ntended for execution only ndicates that the word is IMMEDIATE and will execute during compilation unless special action is taken P Has precedence bit set Will execut ven when compiling U A user variable Group Key Words GROUP The following key words identify the functional group see Appendix A that each word is most related to STACK Stack Manipulation NUMERIC Numeric Representation ARITHMETIC Arithmetic and Logical COMPARISON Comparison Operators CONTROL Control Structures MEMORY Memory I O Input Output FORMAT Output Formatting MONITOR Monitor COMPILER Compiler Text Interpreter DICTIONARY Dictionary Control DEFINING Defining Words VOCABULARY Vocabularies MASS Mass Storage MISC Miscellaneous and System SECURITY Security PRIMITIVE Primitives ASSEMBLER Assembler Dictionary PARAMETER Parameter Used in FORTH WO RD i S CSP STACK NOTATION DEFINITION GROUP ATTR n addr MEMORY store Stores 16 bit number n into addr c SECURITY store CSP Stores the stack position in CSP Used as part of the compiler security See CSP udi ud2 FORMAT W sharp Generates the n
124. ARNING GI 384 367 364 35D F 35A9 IFR 35 354 34E 8 PD A 4 BANKEXECUTE S 8 NMIVEC F C CON 33E C INDEX o O i U 0 0 E BORT MPTY BUFF ERS s gd CO e ot 1 EM BLER zu HW ERPRET 4 D D CODI D B Q MP J gt 4 WORD COUNT BORT GI PAIRS 6 CSP C LFA QE SPACI GI 25C D lt 25A8 C 256 251 250 24C 249A 6 246 0 G 2 0 PAD 9 KHZ ADERLESS 23F Fig 3 VL 4 2 3805 3664 BANKEEC 361E 35D1 3590 356C 3538 34AC 33A0 3384 3368 32CF 3279 3226 1 ES 30BC 305F 3036 DI 2FED 2FOF 2E69 2D72 FLUSH UPDATI MOD GI 2CEA 2CC9 2C1D 2BCS 2B02 QUIT FORTH 2STACK 29F1 CREATE 2949 288B 2846 D 27Fl 27C FIND HOLD DOES gt 2771 MAL 272D 26CC 2670 262A EXEC PFAPTR LATEST 25E4 PICK 25C7 2595 2551 2915 U lt ALLOT 1 24F0 LIMITI
125. ASS to line Places the following text on line n of the current Screen as designated by SCR WORD STACK NOTATION DEFINITION GROUP ATTR gt R Mossas STACK to R Removes a number from the computation stack and places it as the most accessible number on the return stack Use should be balanced with R gt in the same definition addr MEMORY question mark Displays the value contained at the address on the top of the stack in free format according to the current BASE Uses the format of COMP SECURITY Issues error message if not compiling CSP SECURITY Issues error message if stack position differs from value saved in CSP ERROR SECURITY Issues error message 1 STACK EMPTY if the Boolean flag is true EXEC SECURITY Issues an error message if not executing KERNEL gt DICTIONARY question kernel Tests name following an input stream for code being inside or outside the RSC FORTH kernel IN or OUT is displayed accordingly PAIRS Min Aa SECURITY Issues error message 19 CONDITIONALS NOT PAIRED if nl does not equal n2 The message indicates that compiled conditionals do not match WORD STACK TERM NAL ABORT ADMP AGAIN STACK NOTAT
126. AUTOSTART in action First start fresh by entering COLD Then type FORGET TASK HEX 600 H C RETURN Notice that the codes are listed starting at 404 This is because at reset RSC FORTH reserves the first four bytes at 400 for an autostart vector to be added later Now enter this program PROGRAM 0 BEGIN 1 DUP RETURN AGAIN Test the program by entering PROGRAM but be ready to press reset because this is an endless loop PROGRAM displays all the possible numbers starting from 1 Now prepare PROGRAM for autostart by entering 400 AUTOSTART PROGRAM RETURN This sets up the autostart pattern in memory 400 pattern by performin 4 Now press reset PROGRAM cause a cold reset of the Development ROM dedicated application control g 00 20 DUMP RETURN PROGRAM wi from runnin application RAM too PROG SK NTERFAC NG Perhaps the disk handl four quad density 5 1 4 or 3 virtual disk memory 1K byte bl As is comn of bytes called Blocks number of sides per disk 6 4 1 High Level er This firmware all 11 run automatically g is to turn off power and turn it on again was an exampl In PROGRAM fact Look for the autostart the only way to stop This will e of a program Although it has no real world autostarting code it nicely demonstrates target compiled k only 16
127. Ai IU oe 7 18 749 L Assembler Wests ec M ERES E es tee e RR as 7 18 1584 2 Bypassing Security tt e kids 7 18 7 9 Adding Assembly Code to Defining Word 7 19 vii Section 8 9 10 TABLE Or CONTENTS Title Handling Interrupts in FORTH 8 1 Types of Interrupt Handlers e ie RET da 8 2 Machine Level Interrupt Handling 9 251 lt CODESDEEINTELOM ROEM a a eee ares 984242 Code Fragment POP lex oa eee es eee RUNE 8 3 Interpretive Interrupt Handling e 3 1 Interrupt Service Subroutine eiii caw aes 8 3 2 Interrupt Processing Word sews dae e erg Sula Eam p her 23 Aes Akad Ld Me SA v sue Nose Wise att i ee E lees Ere o 8 344 Points bo REMEMBEE Zzoelemo eR n ce bets E RI ere ele Ere Programming the R65F11 I O in FORTH 9 l Parallel 1 0 src as oe tae bee CR NUR aa deo QD ASSET sus ets esas Ate ae M Yo uo Teh e via eb 9 3 Counter Timers 9 9 34 32 Counter A Counters Notes on Style and Program Development 10 1 General 10 2 Example Program Preparing an Application Program for PROM Installation 11 1 Program Development 12 1 Overview 12 zx 12 3 2 Interfacing to Mass Storage 12 2 Setting up Block and Data 1 Mass Storage Terminology Buffer Variables viii Page
128. C leaves 2 on the stack and also sets the address mode to X Here is a pictorial representation of the parameter stack in z page see Appendix F Low Memory TOP low byte lt 0 X the X register points to here TOP high byte lt 1 X SEC low byte 2 X SEC high byte amp 3 X 00C2 The 0 or 2 left by TOP or SEC is the base address above which X register indexes You may further modify this at assembly time to address at any byte in the parameter stack Here is an example of assembly code to or together the top four bytes on the stack FORTH Conventional Assembler TOP LDA LDA 0 X TOP 1 ORA ORA 1 X SEC ORA ORA 2 X SEC 1 ORA ORA 3 X To obtain the 14 th byte on the stack use TOP 13 LDA 7 4 2 Return Stack The FORTH Return Stack and the machine stack is located in the R6500 machine stack area in Page Zero It starts at SOOFF and builds physically downward No lower bound is set or checked This implementation has sufficient capacity for most non recursive applications with 30 levels of entry By R6500 convention the CPU s S register points to the next free byte below the bottom of the Return Stack The byte order follows the convention of low significance byte at the lower address Return stack values may be obtained by PLA PLA which will pull the low byte then the high byte from the Return Stack To operate on arbitrary bytes the method is a Save X
129. CH and leaves addr2 of the reserved offset The stack values will be resolved by REPEAT WORD WIDTH WORD XOFF XON XOR STACK NOTATION DEFINITION GROUP ATTR addr SECURITY U width Leaves the address of user variable containing the maximum number of letters saved in the compilation of a definitions name It must be 1 through 31 with a default value of 31 The name character count and its natural characters are saved up to the value in WIDTH The value may be changed at any time within the above limits char COMPILER word Receives characters from the input stream until the non zero delimiting character in the stack is encountered or the input stream is exhausted ignoring leading delimiters The characters are stored as a packed string with the character count in the first character position The actual delimiter encountered char or null is stored at the end of the text but not included in the count If the input stream was exhausted as WORD is called then a zero length will result LI MONITOR X off Sends XOFF 13 character to system terminal M MONITOR x on Sends XON 11 character to system terminal IL ne nS ARITHMETIC x or Leaves the bit wise logical exclusive or of two values COMPILER left bracket Ends the compila
130. D PRINT D DE A common style is to have only the colon the word being defined and the comment on the first line then indent subsequent lines three columns If the comment is too long put it on the second line There is no compiled code penalty for including comments and spaces so they can be used freely to improve readability when preparing object code for mass storage or if a listing is being made of the source When interactively entering commands from the keyboard comments are not very useful When there is more than one input or output in a command the right most numbers are toward the top of the stack A comment for a definition of a multiply operation might therefore be MPY N1 N2 MULTIPLY amp PRINT EMB J Note that an empty comment must consist of at least a left parenthesis two Spaces and a right parenthesis The reason is that the parsing word WORD in FORTH skips over leading occurrences of the delimiter So if you leave only one Space as in C the first character encountered by WORD is the right parenthesis therefore the system skips it and continues looking for another right parenthesis 4 5 EXECUTING AND COMPILING USING SOURCI GI Up to now you have been operating in a manner where FORTH operations are compiled or executed immediately upon entry in an interpretive mode If a new FORTH word is formed using a colon definition see Section 4 4 the w
131. DE will unsmudge the most recent CURRENT vocabulary definition making it available for execution END CODE also exits the ASSEMBLER making CONTEXT the same as CURRENT addr 2 assembly time iin run time CONTROL end if Another name for THEN addr 2 assembly time CONTROL cc addr 2 run time if Occurs within a code definition in the form cc IF true part ELSE false part THEN WORD Cont E E z STACK NOTATION DEFINITION GROUP At assembly time IF creates an unresolved forward branch based on the condition code cc and leaves addr and 2 for resolution of the branch by the corresponding ELSE or THEN Conditionals may be nested At run time IF branches based on the condition code cc 0 lt or 0 or CS If the specified processor status is true execution continues ahead otherwise branching occurs to just after ELSE or THEN when ELSE is not present At ELSE execution resumes at the corresponding THEN addr assembly time REGISTER i p Used in a CODE definition in the form IP STA or IP Y LDA At assembly time a constant which leaves the address of the pointer to the next FORTH execution address in a colon definition to be interpreted At run time
132. EXPECT 12345678901234 50K HEX 600 10 DUMP OK EXPECT FORTH will wait for your ETURN gt to end the input early Notice 000 31 32 33 34 32 36 37 38 39 30 31 32 33 34 3 0 Use TYPE to display the input data as it was entered HEX 600 DECIMAL O Lo GR TYPI 12345678901234 CI AN 50K Using the two preceding examples as a guide set up an input of 40 characters and display it in HI EX and in ASC 4 13 3 Test for Character Input with TERM NAL The word TERMINAL tests the terminal keyboard and leaves a true flag 1 on the stack if any key is depressed An exampl depression is ANY KEY BEGIN TERMINAL UNTI le of a word that waits for a key This page is intentionally left blank ADVANCED OPERATIONS 5 1 OTHER SINGLE PRECISION ARITHMETIC OPERATIONS There are other FORTH arithmetic words that perform simple operations While these words are not required for many elementary arithmetic operations they simplify implementation of more complex functions 5 1 1 Modulus Operators MOD and MOD The word MOD takes a dividend second on the stack and a divisor top of the stack and leaves only the remainder of a division on the stack for example 22 7 MOD lt RETURN
133. G The FORTH environment s convenient and powerful debugging and error control features are an important advantage of the system FORTH allows complete access to the machine without the restrictions of many other languages such as BASIC and Pascal which try to guard the programmer against mistakes Most users report that FORTH allows them to quickly produce and modify programs which are exceptionally reliable Although RSC FORTH includes extensive compile time checking which detects most of the detectable errors see Appendix E the most important error control is in the tools which the FORTH environment itself gives to the programmer Like most other modern languages FORTH encourages structured programming design techniques which helps to control errors FORTH is extremely modular even compared to other structured languages each software module can be tested and debugged independently Usually all communication between a module and the outside world is through an internal stack Each module relies on earlier modules which have already been debugged and in turn the new testing helps catch any errors that may still be hidden in the earlier work Testing is immediate and interactive simply type arguments onto the stack execute the word and output the results If more elaborate test data is needed a special word can generate it This ease of testing means that a large number of tests can be run
134. H from the compiling state to the interpreting state so that the word SMUDGE will be executed which makes the name of T available in the FORTH dictionary In order for the interpretive interrupts to work the code field address CFA of the interpretive interrupt word must be loaded into NTVEC This is accomplished in this example by the following T Obtain the PFA of T CFA Change it to the CFA ASSEMBLER Switch to the FORTH assembler vocabulary NTVEC Obtain the address of INTVEC Store the CFA of T in INTVEC FORTH Return to the FORTH only vocabulary which follows the definition of T Note that if the microcomputer is executing machine code for an appreciable amount of time and not frequently executing NEXT the FORTH interrupt routine will not be executed and interrupt requests may pile up or be lost depending on t WwW he interrupt service subroutine This can happen when using the printer or aiting for a key The proper choice of machine level or interpretive or both interrupt service routines can make a very flexible approach to control situations or understanding computer interrupts 8 3 4 Points to Remember a Define and code all required words before loading NTVEC or requesting an interpretive interrupt The required CODE words are see text for more detail
135. HEN repeatedly tests whether temperature or voltag xceed their limits xecutes predefined operations GO SLOWER or GO FASTER accordingl 4 8 2 Nesting Control Structures The previous example shows that control structures can be nested an xs LOOP Any of FORTH s control structures can be nested within any other to any practical depth The recommended coding ELSE THEN is inside a DO technique is to keep each definition short and simple operations into two or more s nesting is not normally used ho F like GO SLOWER and GO FASTI is best to define them as separate words to avoid cluttering a singl many levels of nesting Also I VOLTAGE GO SLOWER GO FASTER and HOT may not exist in final he overall design of the control loop the programmer experiments with t t and y breaking complex IF rter ones For this reason great depth of or instance in the examples above operating ER may themselves contain complicated control it e word with his is an example of top down coding as G ET E form yet as Of course GET VOLTAGE GO FASTER and HOT must exist in some form at least before the loop would compile in a definition If not the first unknown word name encountered would cause the error message name to be output Another recommended coding style is to indent IF T
136. HEN or IF THEN ELSE like DO LOOP Keep the whole structure on one line if it is short enough otherwise indent the IF ELSE if present and THEN to line up vertically Each new level of nesting structure should be indented at least one space 4 8 3 Masking and Setting Bits The operations used for masking selecting certain bits within a 16 bit word and turning them OFF or ON or complementing or testing them were largely covered in Section 4 7 3 This section further explores these operations in many of the control applications to which the R65F11 and R65F12 microcomputer is well suited Mask values are best presented in hexadecimal In hexadecimal the values 0000 through FFFF can be input a minus sign can also be used to input numbers 8000 to FFFF 8000 to 1 The dot period works for output but if the first bit is set use the phrase 0 D zero double precision print instead to avoid having the number interpreted as negative This makes the top stack item a double integer whose most significant 16 bits are zero and then uses the double integer print word to output the resulting positive 32 bit integer In the following examples we will be changing or testing the last three bits of a word i e the mask value will be 0007 last three bits set all others off This value could be written simply as 7 but the leading zero
137. K Verify this by typing S and RETURN to show the new contents of the stack 44 333 22 1 OK The next dot and lt RETURN gt will print the 44 Multiple commands separated by spaces can be typed on one line like this RETURN to display two numbers from the stack e g RETURN 333 22 OK Now only 1 is left on the stack Output it with RETURN which displays 1 OK Trying to examine or print the stack contents when there are no numbers on the stack will result in an error message Try S which will show S RETURN EMPTY OK Note that the word will now cause a stack underflow and will display an indeterminate value along with a stack empty message Try it now O typical number STACK EMPTY Similar FORTH operations trying to pull a number from an empty stack will result in this error message This error message as well as others are described in Appendix E Notice that the data was displayed on the same line as the commands i e the FORTH word in this case Many times it is desired to display and print data on a new line The FORTH word CR issues a carriage return to the terminal Repeat the previous examples but insert CR before the word and note that the numbers are displayed on separate lines Also try CR after the and observe the results Perform a cold restart before continuing COLD RSC FORTH V1 6 4 1 3 Clearing the Stack
138. KS 1 C PLCKS 24 E 0 TICKS 3 MIN LOA El C ER O 100THS T S P TIME amp GO T INIT C CON PINUOUSLY DISPLAY MST amp TIM BEGIN 24 EMI B LANK CURSOR 13 EMI n STAY ON LINE D T UNTIL 23 EMI D R D QUIT DISPLAY MSG amp R ESTORE CURSOR IME ONC E Figure J 1 M Lu ERMINAL QUIT r 24 Hour Clock Program Using a Machine Interrupt Handler Cont d J 4 BL BH ERIODL ERIODH CONS CONS CONSTANT P CONSTANT P o VARIABL VARIABL DAYS TICKS LEE RI 2 BYTES 4 BYTE o DE ISABLE DISABLE D L STA J lt W T D COD UHZHOO H A AOO MACHINE ASSEMBLE PHA CODE INT R HERE SAVE IRQ ERRUPT SE RVICE VECTOR r 80 LDA S INTFLG ORA INTFLG STA TBL LDA PLA IRORTN JMP CLEAR US E R VIA R E ET INT REQUEST IRQ TURN TO I O ROM CODE ARM RETURN E FROM FORT H INTERRUPTS BF LDA RESE INTFLG AND INTFLG STA INT REQUES BIT S JMP RESTORE ERRUP ED IP END CODI e
139. M 65 40 and IM 1 Microcomputers for a memory dump The primitive used by ADMP to output an individual record is DUMP Both words are easily exercised DUMP requires two parameters from the stack the starting address and the number of bytes to dump To test it try dumping a record that contains the first few bytes of the Development ROM with DUMP and DUMP HEX CR 2000 10 DUMP 2000 5A A5 6E 2C FF FF FF FF 40 1 F8 17 0 20 0 0 OK CR 2000 10 DUMP 1020005AA56E2CFFFFFFFF4001F817002000000735 OK Now try AD ending addr MP ess 2000 207F OK ADMP 718200 7182018000000003C0381A00404000081A0C73F36034 718203 182048F4864252414 18206086284C4F4F50A95420 08207828444F196B20FAF4047D 0000070007 OK 6 5 4 Using EEC to Program a PROM over a larger area of memory E P Although it may be quite convenient to use commercial particularly when the program ll or R65F1 permanent program storage the addressing space available on the R65F1 It is possib EROMS directly in circuit not always program EPROMs or E readily available ADMP requires a starting and 05AA56EZCFFFFFFFF4001F817002000001F0000000404 0000010F484434C49D42C205AF487455845435554C534 E43C83D2082F4873042524141 B1F487282B4C4F 4F50A96020D2F4840AC9 is 111040779 E2C834C49D0467E 120730917 43C8492
140. N RSC FORTH SCREEN NUMBERS VERSUS TRACK NUMBERS The RSC FORTH disk operating system is designed to operate with up to four double sided quad density 5 1 2 inch or 3 1 2 inch disk drives 80 track This provides the capability for over 2 5 MB of on line storage Smaller disk drives may still be used however The FORTH SCREEN numbering scheme must be considered for different size drives When using smaller drives there will appear to be holes in the screen numbers For example drive 1 normally contains screens 640 through 1279 If a 40 track double sided drive is substituted the screens will now range from 640 to 799 on side 0 and from 960 to 1119 on side 1 Figure N 1 shows the boundary starting screen numbers for 40 and 80 track disk drives First Screen No First Screen No uro wae ELAS Figure N 1 First Screen No Versus Track No N 2 APPENDIX O RSC FORTH EDITOR This appendix lists a FORTH Editor that will operate with RSC FORTH gt G0 0 NO ADN gt a gt gt bh Hh nn UC tfo 090 NO 0 5 uNa O em m m m m SCR leoFORTH Editor Load Block public domain editor compatib written by Sam Daniels modified amp extraneous garbage modified to RSC Forth compati VOCABULARY EDITOR IMMEDIATE 7 7 LOAD 74 75 THRU C com EDITOR DEFINITIONS 74 LOAD Match 2 FORTH DEFI
141. NEXT moves IP ahead within a colon definition Therefore IP points just after the execution address being interpreted If an in line data structure has been compiled i e a character string indexing ahead by IP can access this data IP STA or IP Y LDA loads the third byte ahead in the colon definition being interpreted AI MISC memory Used within the assembler to set MODE to the default value for direct memory addressing on z page WORD NOT POP POPTWO STACK NOTATION DEFINITION GROUP addr assembly time REGISTER yw Used in a CODE definition in the form N1 STA or N 2 Y ADC A constant which leaves the address of a 9 byte workspace in z page Within a single CODE definition free use may be made over the range N 1 thru N 7 See SETUP addr assembly time RETURN next A constant which leaves the machine address of the FORTH address interpreter All CODE definitions must return execution to NEXT or include code that returns to NEXT i e PUSH PUT PUSHOA PUTOA BINARY POP POPTWO ccl cc2 assembly time CONDITION not When assembling reverse the condition code for the following conditional For example O NOT IF lt true part gt THEN will branch based on not equal to zero NOT is not valid for BITCLR or BITSET reversa
142. NITIONS C SCR leoFORTH Editor Line Text LINE C line addr J SCR Q CLINE DROP TEXT 06 put text u 58 24 FEB 83 MWR le with Starting Forth J removed by Dave Boulton J bility by MWR 3 patibility J 64 68 THRU t Editor words 78 LOAD C New J 72 LOAD C Bulkclear wipe J 73 LOAD 76 LOAD Copying stuff n 54 Cursor Use 24 FEB 83 MWR J 041 o te PAD 3 HERE 65 BLANKS WORD HERE PAD 65 CMOUE 3 VARIABLE RU C curs 94 CONSTANT DELIM C for text 4 mn S CURSOR DELIM EMIT E SCR leoFORTH Editor fiLead Llaga HLOCATE C H linen Ru e C L mO0D HLEAD C addr i HLOCATE LINE SWAP 3 LAG C addr LEAD DUP DR C L R MOVE C addr linet LINE C L CMOVE UPDATE 1 BUF MOVE C addr mo PAD 4 C IF PAD SWAP C or position J delimiter t 62 Move 24 FEB 83 MUR J give cursor position string before cursor posn J string after cursor posn E fill tine from addr ve PAD to addr if non null J L 4 CMOUE ELSE DROP THEN gt LINER C line give line ff of cursor posn J HLOCATE SWAP DROP 3 FIND BUF PAD 880 3 INSERT BUF PAD 4168 7 Figure 0 1 RSC FORTH Editor 0 2 3 X ER KKK KEK KK X X X OX KEK OK X OX CX OX OX OX KK X X X X X X X OX OX OK X OX OX OX OX X koX 0 N40 b OT G0 SCR Y 63 leo FORTH Editors Hold Kill etc 24 FEB 83 MUR C HOLD 3 C linett move line to insert buffer LINE INSERT BUF 4
143. RMAT hold Used between lt and gt to insert an ASC character into a pictured numeric output string WORD HWORD STACK NOTATION DEFINITION GROUP ATTR M as DICTIONARY h word Latest defined word s code section is lifted from codes dictionary relinked and placed in the heads dictionary Dictionary pointers are re adjusted accordingly ER OUR CONTROL wow Used within a DO LOOP to copy the loop index from the return stack to the stack nfa INPUT OUTPUT i d dot Prints a definition s name from its name field address See NFA addr MISC P interrupt enable register System address constant for addr of Interrupt Enable Register flag run time CONTROL addr n compile if Used in a colon definition in form TIBUS vus THEN TES n t ELSE RU THEN At run time IF selects execution based on a Boolean flag If flag is true the words following IF are executed and the words following ELSE are Skipped The ELSE part is optional If flag is false the words between IF and ELSE or between IF and THEN when no ELSE is used are skipped F ELSE THEN conditionals may be nested At compile time IF compiles OBRANCH and reserves space for an offset at addr Addr an
144. RRAY type DECIMAL HERE to s where the next dictionary entry will occur Then enter 50 ARRAY X HERE to how much dictionary space has been used by the array Note that there are 10 bytes of overhead plus the 100 bytes for the array If you now enter 10 ARRAY Y HERE you will see that 20 bytes of array plus 10 bytes of overhead has been allocated Entering 1234 5 X will now store 1234 in the fifth element in the X array And entering 5 X will now place 1234 on the top of the stack The data to go in an array may be loaded at compile time by the following technique VECTOR BUILDS 0 DO LOOP DOES gt SWAP 2 The data on the stack is in inverse order and the top value on the stack is the number of elements in the vector Thus Data n 1 data n 2 data 0 n VECTOR ALPHA creates a vector with n elements called ALPHA For example 55 4444 33 2222 1111 0 6 VECTOR ALPHA Now check the element data 3 ALPHA RETURN 33 O ALPHA RETURN 0 2 ALPHA 8 RETURN 2222 These elements may be changed if so desired if the dictionary is in RAM e g 1010 0 ALPHA Check with O ALPHA RETURN 1010 In the definition of VECTOR a loop is executed the number of times indicated by the top value on the stack The only function performed by the loop is to use the command to store the current top va
145. RSC FORTH User s Manual d 29651N51 Rockwel Order No 21 91 ou PREFACE This manual describes the operation and use of the Rockwell Single Chip FORTH system as implemented in the Rockwell R65F11 40 pin and R65F12 64 pin FORTH based one chip Microcomputers and in the Rockwell R65FR1 FORTH Development ROM RSC FORTH herein without notice This document is sub O Rockwell U S A ii NOTICE Rockwell International does not assume any liability arising out of the application or use of any products circuit or software described herein neither does it convey any license under its patent rights nor the patent rights of others Rockwell International further reserves th right to make changes in any products ject to change without notice International Corporation 1983 All Rights Reserved Printed in Section 2 3 TABLE OF CONTENTS Title Introduction 1 1 RSC FORTH User s Manual Description 1 2 REES LENCE Poc ments tota le es ss A ida cs Functional Description Jed RSC EORTH Hardware da 2 1 1 R65F11 and R65F12 Microcomputers 2 1 2 Configuring an R65F11 R65F12 Based System 222 RSESEORTA SOLUWADES e dre wr id ur dur IA ta ue es 2 82 1 Operating SY SEEM uuu ota a ete 2 2 2 Application Program A uto Statt iili 2443 Development ROM Startup sreng RES an 2 2 44
146. TA Addresses the second 16 bit item on the data stack by selecting the X X address mode and leaving 2 on the stack addr assembly time STACK setup A constant whose value is the address of a utility routine to move items from the stack to the N area of zero page The number of items to move 1 2 3 or 4 only is in the A register addr 2 assembly time CONTROL run time then Occurs in a CODE definition in the form E z 4 cc IF true part ELSE false part TH WORD THEN Cont TOP UNTI STACK NOTATION DEFINITION GROUP At assembly time THEN marks the conclusion of a conditional structure The conditional branch instructions generated by IF and the JMP instruction generated ELSE point to the instruction immediately following THEN When assembling addr and 2 are used to resolve the pending forward branch to THEN GI At run time THEN marks the conclusion of a conditional structure Execution of either t true part or false part resumes following THI 0 zi z lt 0 assembly time STACK Bop Used during code assembly in the form TOP LDA or TOP 1 X STA Addresses the top of the data stack containing the low byte by selecting the X mode and leaving n 0 at assembly time This value of n may be modified to another byte offset
147. The output shows the blanks ASC 20 the 15 OOOF stored as a word with the bytes reversed by the 6502 CPU so it looks like OFOO and the 15 F stored as a byte 10 bytes later The 10 shows use of an offset to an address this technique can be used to create data structures such as arrays records and fields etc 4 9 3 Increment Memory with A very useful memory modification word is pronounced plus store takes a stack value and a memory address and adds the value to the contents of the address for example it is used for incrementing counters in memory Define the word BUMP to increment the contents of address 600 by one eight times and prints the contents of 600 after each increment HEX BUMP CR 80 DO 1 600 600 C LOOP Initialize 600 to zero and execute BUMP 0 600 C BUMP 1234567 8 OK Try it again but first initialize 600 to 10 10 600 C BUMP LL T2 3 A 5 T6 IY X9 OK Define another function UPBY6 to increment the memory contents by six and display the results UPBY6 CR 8 0 DO 6 600 600 C8 LOOP Clear 600 contents and try it 0 600 C OK UPBY6 6C 12 18 1E 24 28 30 OK 4 9 4 Exclusive OR Memory Using TOGGLE TOGGLE takes an address and a one byte mask as arguments it does an exclusive OR between the byte and the address contents updating the latter Experiment with TOGGLE by first i
148. UT OUTPUT type Transmits n characters beginning at addr to the active output device No action takes place for n less than one unl un2 ud ARITHMETIC u times Performs an unsigned multiplication of unl by un2 leaving the unsigned double number product of two unsigned numbers ud ul u2 u3 ARITHMETIC u divide Performs the unsigned division of double number ud by ul leaving the unsigned remainder u2 and unsigned quotient n3 from the unsigned double dividend ud and unsigned divisor ul unl un2 flag COMPARATIVE u less than Leaves the flag representing the magnitude comparison of unl un2 where unl and un2 are treated as 16 bit unsigned integers addr PARAMETER U u abort Leaves the address of the user variable containing the code field address of the ABORT word addr PARAMETER U u characters per line Leaves the address of the user variable containing the number of characters per line addr PARAMETER U u first Leaves the address of the user variable containing the first address of the data or mass storage buffer WORD ULIMIT UNTIL UPAD UPDATI GI UR W STACK NOTATION DEFINITION GROUP ATTR addr PARAMETER U u limit Leaves the address of the user variable containing the last address plus one of the data or ma
149. W The words SELECT SEEK DREAD DWRITE DISK and INIT are all in the kernel The variables DISKNO CYLINDER and B SIDE are not but are referred to where needed by actual address in page 3 6 5 GENERAL UTILITIES 6 5 1 Formatting a Disk A number of words best described as utilities have been added to RSC FORTH to allow more complete use of the facilities of a single chip application Two are directly related to disk operations The code required to format a disk is quit xtensive over 300 bytes For that reason the format routine is not in the kernel but in the Development ROM instead FORMAT formats a complete disk on both sides Two parameters must be passed to FORMAT the drive number to format on the top of the stack 6 9 and the number of tracks to format second on the stack FORMAT calls a lower level primitive FMTRK which formats a single track Although it is doubtful that many will use this primitive directly it is available for execution 6 5 2 Screen Modification Although most standard FORTH systems allow examination of mass storage by block with words like LIST NDEX and LINE few if any have words that allow the blocks to be modified Normally you must load a screen editor to perform such functions RSC FORTH has a utility word added to allow simple screen modi
150. W RAM Block No Update Flag Address returned by BLOCK Block Buf fer Data 00 lt Null character Null character 00 Data Buffer The RAM area reserved for use by mass storage commonly called the data buffer area or the mass storage buffer area must contain two or more of the block buffers described above The first byte of the entire mass storage buffer area is referenced by the word FIRST and is stored in the variable UFIRST The last byte of the entire buffer area is located at LIMIT 1 and the value returned by the word LIMIT is kept in ULIMIT The layout of the buffer area is LOW RAM FIRST Block Buffer 1 Mass Block Buffer 2 Storage Buffer Block Buffer 3 Block Buffer n LIMIT 12 2 C Screen Size Conventionally when a screen of source code is listed on a CRT display it appears as 16 lines of 64 characters each The lines are numbered 0 to 15 on the left of the text 12 1 2 Buffer Variables The number of blocks and the size and location of the data buffer in RSC FORTH is controlled by two user variables UFIRST and ULIMIT The logic of which one to use at any given time is controlled by three other variables PREV USE and OFFSET The names description and access words for these variables are given in Table 12 1 12 2 SETTING UP BLOCK AND DATA BUFFERS
151. WIPE LOOP 3 BASE 7S SCR amp 73 EDITOR 43 day year month 24 FEB 83 MUR 3 BASE HEX DAY RH e 2E RH 2 DELETE I RH 1 3 YEAR RN e 35 RA 2 DELETE I RB 3 MONTH RH G 32 RM 3 DELETE I RH 5 O SCR SWAP SCR L 3 BASE 1S SCR N 74 C LeoFORTH editor compatibility to rdcFORTH 24 FEB 83 MUR BASE HEX ASCII BL WORD HERE 4 C8 CCOMPILE LITERAL IMMEDIATE CODE i TYA TOP 4 CMP IF INY TYA TOP CMP NOT IF DEY THEN THEN TYA PUT A JMP END CODE BEEP 7 EMIT 5 TRIAD 3 3 3 OVER SWAP DO CR I LIST LOOP CR GF MESSAGE CR BOC EMIT BASE 3S Figure 0 1 RSC FORTH Editor Continued 0 6 X XX X 0X 0X OX 0X CX OX OX OX OX OX X X X X X X SE SE SE OX CX CX Ok X X HK ox SCR Y 7S A de c e e e Q1 4 0 I o O 00 0 OS NADA O DOCUMENTATION SCREEN 24 FEB 83 MUR 4 BASE HEX 2 SHOW 3 1 3 SWAP DO I TRIAD TERMINAL IF LEAVE 3 THEN 3 LOOP 5 4 BASE 1S S 6 7 8 9 SCR U 76 C EDITOR 88 rep backup 24 FEB 83 MWR 3 BASE DECIMAL COPY DUPLICATE SCREEN 2 ONTO SCREEN 4 41024 byte buffers SWAP BLOCK 2 UPDATE 3 REP C Replicate screen 1 to blckH on 2 drive J DUP 640 COPY 3 BACKING C part of a disk 8 FLUSH CR DO FORTH I DUP REP C LIMIT FIRST B BUF 4 J C number of buffers J LITERAL MOD B IF FLUSH THEN LOOP FLUSH BEEP 5 BACKUP C all of a disk 640 BACKING 5 SYSTEM BACKUP C the system code only 378 BACKING BASE
152. X A constant which leaves the address at assembly time of a temporary buffer for saving the X register Since the X register indexes to the data stack in z page it must be saved and restored when used for other purposes This page is intentionally left blank APPENDIX E ERROR MESSAGES AND RECOVERY T E 1 STANDARD ERROR MESSAG The standard FORTH error message is This question mark is output along with the most recently interpreted word when that word can not be found in the dictionary and will not convert into a number in the current BASE For example RSC FORTH V1 6 QUERTY QUERTY ABC ABC HEX OK ABC OK DECIMAL lt RETURN gt 2748 OK Upon initialization QUERTY and ABC were not in the dictionary therefore the error message was displayed when they wer ntered After the number base of the I O was changed to HEX however ABC became a valid number ABC was then accepted as a valid number upon the record entry attempt converted to internal two s complement binary format and stored on the stack The number was then removed from the stack and displayed in decimal E 2 STANDARD ERROR MESSAGE WORD RSC FORTH has a standard error message word ERROR which takes two items from the stack t n ERROR where t is Boolean and n is the desired error number
153. Y lt RETURN gt lt input character gt DECIMAL A word can easily be defined to display the entered number in both bases ASC KEY DUP DUP CR EMIT HEX DECIMAL The input procedure is ASC RETURN character Try it with a couple of numbers ASC RETURN A A will not be displayed A 41 65 ASC RETURN 1 1 31 49 ASC RETURN 3F 63 Experiment with a few other numbers and compare your results with Appendix H 4 13 2 Input a String from the Terminal with EXPECT The word EXPECT accepts a one line string from the terminal EXPECT takes two arguments from the stack a starting address in RAM and a maximum length of the input string it returns no result to the stack When executed EXPECT waits for the terminal input it keeps accepting characters until you press RETURN or until the maximum length is reached Note that EXPECT terminates the input string with a null byte 00 be sure there is room for it in the input area For example us EXPECT to prepare to input 15 characters enter the data then dump the input data in hexadecimal input data see Appendix H input 15 characters maximum which represents the ASC code for the After you type Press Rl that the last byte dumped is the null byte HEX 600 OK DECIMAL OK 15 CR
154. a part of FORTH until a differing CURRENT vocabulary is established User vocabularies conclude by chaining to FORTH so it should be considered that FORTH is contained within each user s vocabulary nl n2 MASS format track Format track nl on side n2 of the selected disk B 30 WORD H C ESS HLD HOLD STACK NOTATION DEFINITION GROUP ATTR addr DICTIONARY h slash C Separates heads and codes dictionary Heads are set to generate at addr DP is assigned this addr Codes are set to generate at value of DP prior to execution HEADERLESS is set to 1 Results are displayed for verification addr DICTIONARY headerless User variable containing boolean flag indicating state of target compilation When equal to 0 normal code is compiled When equal to 1 headerless code is compiled addr DICTIONARY here Leaves the address of the next available codes dictionary location addr DICTIONARY here slash Leaves the address of the next available dictionary in the heads dictionary NUMERIC hex Sets the numeric conversion BASE to sixteen hexadecimal addr FORMAT hold Leaves the address of user variable which holds the address of the latest character of text during numeric output conversion char FO
155. acters of text or until a return from the keyboard into the terminal input buffer TIB WORD may be used to accept text from this buffer as the input stream by setting IN and BLK to zero MISC quit Clears the return stack stops compilation and returns control to the keyboard No message is given se STACK EN Copies the top of the return stack to the computation stack addr blk flag MASS r slash w The mass storage read write linkage addr specifies the source or destination block buffer blk is the sequential number of the referenced block and flag specified read or write flag 0 is write and flag is read R W determines the location on WORD R W Cont R RO EAT ROT RP RP STACK NOTATION DEFINITION GROUP ATTR storage performs the read write and performs any error checking R W executes the cfa found in UR W On cold start this is the address of ABORT Al STACK r from Removes the top value from the return stack and leaves it on the computation stack See gt R and R addr PRIMITIVE U Y zero Leaves the address of user variable containing the initial value of the return stack pointer See RP addr n compiling CONTROL repeat Used within a colon definition in the form BEGIN WHILE REPEAT
156. ag 1 if nl is less than n2 otherwise leaves a false flag 0 WORD lt ILDS gt LINE STACK NOTATION DEFINITION GROUP ATTR da FORMAT less than sharp Initializes the pictured numeric output format using the words lt 4S HOLD SIGN gt specifies the conversion of a double precision number into an ASC character string stored in right to left order producing text at PAD Used within a colon definition name BUILDS DOES E each time name is executed BUILDS defines a new word with a high level execution procedure Executing name in the form lt name gt lt namex gt uses lt BUILDS to create a dictionary entry for lt namex gt with a call to the DOES gt part for lt namex gt When nnnn is later executed it has the address of its parameter area on the stack and executes the words after DOES gt in lt name gt lt BUILDS and DOES gt allow run time procedures to written in high level rather than in assembler code as required by CODE nl n2 flag COMPARISON equals Leaves a true flag 1 if nl is equal to n2 otherwise leaves a false flag 0 nl n2 flag COMPARISON greater than Leaves a true flag 1 if nl is greater than n2 otherwise a false flag 0 n text M
157. ak al e eo dx Eos Page No Co XO amp O XO XO 00 00 OO iS BN PO b d RO R04 C0 PO PO iO DN or XO XO XO XO xo y cq cu ER 3 RSC FORTH ERRATA RSC FORTH V1 5 The RSC FORTH Version 1 5 V1 5 described in this manual is contained in the following parts R65F11 FORTH Microcomputer R1100 11 or R1100 14 1 MHz or R65F12 FORTH Microcomputer R1200 11 1MHz and R65FR1 Development ROM R2952 12 1MHz Errors in this version can be corrected as follows 1 ADMP leaves two undefined bytes on the stack Redefine the word as ADMP ADMP 2DROP 2 FORMAT is inoperative Redefine the word as FORMAT 2 SWAP 0 DO DUP 1 SELECT I SEEK 1 I FMTRK DUP SELECT 0 I FMTRK LOOP DROP 3 IRQVEC returns the value for INTVEC Redefine the word as HEX IRQVEC 0040 4 I contains a reference to the Development ROM and can not be used in stand alone code Solution is to use R instead 5 NOT contains a reference to the Development ROM and can not be used in stand alone code Solution is to use 0 instead 6 CREATE has an error which can cause the CFA of a word to straddle a page boundary which is an error condition for the 6502 CPU Solution is to test a suspected word with HEX NAME CFA and verify that the address is not XXFF If the address is XXFF the word should be forgotten and a 1 ALLOT inserted before redefining the word xi RSC FORTH V1 6 RSC FORTH V1 6 corrects the ADMP and FORMAT e
158. akes as an example simple problem of figuring the miles a car traveled per gallon of fuel from data kept in a common automobile record book a Problem Definition Start with the definition miles traveled mpg gallons used 10 1 which is fine if you record mileage and gallons and you aren t particular about accuracy For the newer automobiles an error of a tenth of a gallon can cause an error of 0 5 mpg in the result For best accuracy you should accumulate mileage and gasoline used over several fill ups This averages your error in filling the tank non uniformly and then by recording the data carefully you can have an accurate picture of your gas mileage miles amount mpg but gallons _ gallons price SO miles gt miles price mpg amount AAA amount price However miles is not the odometer reading it is the miles traveled and the odometer will require a correction factor so miles m1 m0 k m0 last odometer reading ml current odometer reading k correction factor therefore m1 m0 kp p price mpg a amount a But price is either in cents per gallon or cents per liter and since you are probably interested in miles per gallon you will have to multiply any cents per liter prices by 3 785 to correct to cents per gallon Finally m1 m0 kp mpg for cents gallon a or m1 m0 k 3785p mpg for cents gallon
159. am the second byte with a 55 pattern the following entry is required H EX 55 801 D MAL 10000 EC EEC The first Th E TTL signal assume t are pin and requires and VPP The 2716 lowest on the stack followed by the address that it is to be The top value on the stack is the number of clock cycles to For example 6116 is hat a Rockwell type RAM EMS is low devic is 2K byt The 10000 assumes a 1 MHz clock to give a 10 millisecond programming pulse address 800 a small HEX MOV E TO PROM 800 400 DO ca 400 2710 EC In order to transfer an entire program from RAM at address 400 to E programming word must be entered LOOP EROM at 6 5 5 Bank Switching MOVE TO PROM runs a loop from 400 to S7FF picking up bytes and programming them at addresses 800 to SBFF The data is held stable for 2710 10000 clock cycles Similar words can be made for about any programming requirement using EEC Most dedicated applications will find the 16K byte addressing range of the R65F11 and R65F12 to be quite sufficient that requir ven mor Space Occasionally there will be designs For these occasions RSC FORTH has four words that can be used to bank switch the external memory map to give a virtual memory capability of nearly four megabytes
160. and list of these words is given with definitions in Table 6 1 Thes addresses ar ROM is removed Although none of these system addresses are actual may be used in the development of dedicated application code the defining word used to create the system constants interprets their use differently when compiling Used outside a col becaus perform exactly as constants do Word FU p Hi UU ty U DU UY n Q Hl E CO O0 UJ R ER MCR SCCR SCSR SCDR INTFLG NTVEC ROVEC NMIVEC lear that appl Ly words that lications wh are in the lure when th lly defin lon defin named in RSC FORTH by a special type of defining word Later in this section it will be made cl a target system must reference onl a word not in the kernel will cause system fail addresses C000 to DFFF set to SFF ich are programmed for kernel Referring to e R65FR1 Development ed in the kernel they This is possible ition these words Address 0000 0001 0002 0003 0004 0005 0006 0011 001 001 001 001 001 004 005 004 004 NoOoUP JococuN TABLE 6 1 System Address Constants Function Port A Port B Port C Port D Port E only with R65F12 Port F only with R65F12 Port G only with R65F12 Interrupt Flag Register Interrupt Enable Register Mode Control Reg
161. ariable Use to fetch the data from its address and to put data into its address Any var able can be accessed in this manner the special access words are only for convenience 12 4 12 3 USING MASS STORAGE The simplicity of the disk interface and FORTH s ability to customize to a particular application allows mass storage devices to be easily used in powerful ways Two such ways are described in this section Remember all mass storage operations must use diskettes that are first formatted with either FORMAT or a similar word 12 3 1 Data Storage and Retrieval the Virtual RAM Data storage and retrieval using a mass storage device is quite simple Just think of the data as an array of numbers and given th lement number of a data item in the array compute the required block number and offset into that block Knowing the block number all that is left to do is to access the block and add the offset to the address returned by BLOCK Suppose you want to process an array of 250 16 bit numbers and you wish the data to start at block 25 If the disk uses 256 byte blocks a word that would supply the RAM address of a given array element number 0 249 would look like DATA 128 MOD 25 BLOCK SWAP 2 The address produced by DATA can then be used like any other variable address The normal FORTH words and would then fetch and store data as if it were always in RAM One extra modification would
162. assembly time CONDITION zero equals Specifies that the immediately following conditional will branch based on the processor zero flag status bit being equal to one Z 1 i e equal to zero The flag cc is left at assembly time there is no run time effect on the stack WORD AGAI BITC BINARY LR STACK NOTATION DEFINITION GROUP addr 1 assembly time CONTROL run time again Occurs in a CODE definition in the form BEGIN AGAIN At assembly time AGAIN assembles a JMP instruction to addr The number 1 is issued for error checking At run time AGAIN branches unconditionally to its matching BEGIN addr 1 assembly time CONTROL orem run time Occurs in a CODE definition in the form BEGIN cc UNTIL At assembly time BEGIN leaves the dictionary pointer address addr and the value 1 for later testing of conditional pairing by UNTIL or AGA IN At run time BEGIN marks the start of an assembly Sequence repeatedly executed It serves as the return point for the corresponding UNTIL When reaching UNTIL a branch to BEGIN will occur if the processor status bit given by cc is false otherwise execution continues ahead addr assembly ti
163. ate a constant named n lt name gt name with value n Execution returns value when name n executed CODE name Begin definition of assembly language primitive operation named name CODE mms Used to create a new defining word with execution time code routine for this data type in assembly BUILDS Compilation Used to create a new DOES BUILDS defining word with Execution execution time routine DOES for this data type in higher level FORTH USER Offset user name Create a user variable CASE name Begin case statement definition C CON Compilation Create byte constant named n name name with value n Execution returns address when name address executed A 13 VOCABULARIES CONTEXT addr Returns address of pointer to CONTEXT vocabulary CURRENT addr Returns address of pointer to CURRENT vocabulary FORTH Main FORTH vocabulary execution of FORTH sets CONTEXT vocabulary ASSEMBLER Assembler vocabulary sets CONTEXT DEFINITIONS name Sets CURRENT vocabulary to CONTEXT VOCABULARY name Create new vocabulary named name VLIST omm Print names of all words in CONTEXT vocabulary VOC LINK addr Most recently defined vocabulary A 14 MASS STORAGI GI LOAD screen
164. ating System initializes the serial channel for asynchronous operation with both the receiver and transmitter enabled seven bits per character and no parity Counter Timer A is set to the interval timer With the one exception of the Receiver Shift Register Mode which uses the external clock all transmitter and receiver bits rates occur at one sixteenth of the Counter Timer A interval timer rate Counter Timer A is forced into the interval timer mode whenever one of these other serial modes is selected Counter Timer A must be loaded with the correct value for the desired serial rate The RSC FORTH Operating System sets the baud rate for 1200 baud assuming a 1 MHz internal clock at power up The operator or an application program can change the baud rate to whatever value desired Table 9 4 shows values for standard baud rates The serial channel can be altered to these values as illustrated by HEX XXXX 18 where XXXX is the desired hex value from Table 9 4 and 18 is the address of Counter Timer A The transmitter operation and the transmitter related control status functions are enabled by bit 7 of the SCCR The transmitter when in asynchronous mode automatically adds a start bit one or two stop bits and when enabled a parity bit to the transmitted data A word of transmitted data in the asynchronous mode can have 5 6 7 or 8 bits of data The nine possible data modes are shown in
165. ation Only numbers go on the stack Strings or other data structures do not reside there directly although some data such as pointers addresses length and offset information ASC values are frequently on the stack How many numbers can reside on the stack at one time RSC FORTH limits the stack depth to 50 16 bit values in order to keep the parameter stack in zero page to maximize the R65F11 CPU execution speed Except for certain recursion problems very few programs ever need a stack depth of more than about 20 Operation 42 50 128 1090 3 Stack 2 oni n a ss a o oc 1 Top n 50 s 128 1090 3 363 135 eso 2 42 8 128 1090 1281 8 3 B 128 8 4 8 Figure 4 2 Stack Diagram of Postfix Example 4 1 7 Decimal and Hexadecimal Number Base Up to now we have been working in DECI to b MAT represented in different number bases defined bases now DECIMAL and HEX during initial entry or upon commanding COLD with numeric calculations useful when working with addresses or FORTH allows input and output data We will consider only two pre FORTH is initialized to DECIMAL DECI HEX operates in hexadecimal logical operations on individual base 10 MAL is best used when working base 16 and is most bits Type DECIMAL or HEX to change FORTH to the desired base befor ntering or
166. be appropriate her the word should automatically indicate that data was put into a disk buffer so that the buffer will be written out automatically This is easily done by redefining and as U and Ue value index U DATA UPDATE index value U DATA The actual use of DATA is shown by a couple of examples To print the 153rd number simply type 153 UG To clear out the entire array use CLEAR 250 0 DO O I U LOOP FLUSH The word FLUSH at the end writes all updated buffers out to the mass storage device 12 5 12 3 2 Program Loading and Overlays Once a screen has been written with a FORTH program the program into th screen number from 0 and continues until a at any position will always stop Programs of contiguous more Each and any number of e dictionary Hie PS compiling at the first than one screen may be screen the last screen must be terminated with of the first screen This is done with the stack and begins compiling that screen is encountered LOAD The S words may appear on a Screen S encountered it is necessary to compile which takes the starting at line terminator may be placed but FORTH compiled but only if the screens are except for the last must end with the word gt and 7S Compilation starts with a LOAD in the sequence With a disk connected to an RSC FORTH microcomputer with 18K b
167. be sure to insert a space first A FORTH definition may be continued on as many lines as needed This TEST OP operation takes one number from the stack as we have seen It does not return any result but if the were omitted the product would stay on the top of the stack Note that no formal parameters are used to show the inputs and outputs of an operation These are implicit TEST OP takes one argument because it puts one number 5 on the stack then performs a multiply which uses two numbers the 5 and one other Check the operation of TEST OP by placing a value on the stack and executing TEST OP e g EST OP RETURN 30 OK EST OP RETURN 40 OK 6 TI 8 TI If the word being defined is already in the vocabulary dictionary the message name NOT UNIQUE will be displayed The NOT UNIQUE message is displayed only as a reminder that you have redefined a word which was previously defined and has no effect on the compilation process e g DOTEST COR 0 TEST OP NOT UNIQUE OK Now test it with EST OP RETURN 60 EST OP RETURN 80 6 TI 8 TI Note that only the new definition of TEST OP is found and executed 4 4 2 Find a Word in the Dictionary with Use the word pronounced tick to find if a word is already contained in the dictionary and to return its parameter field pointer address PFAPTR Note This var
168. by the word KEY only by EMIT Now define one word to do both KEY KEY CR EMIT CR Check it with 2KEY lt RETURN gt A A OK KEY RETURN OK Now try a few other characters of your own choice try lower case letters also 4 12 4 Output a String with TYPE To display an ASC string given its address and length length on top of the stack use TYPE Try HEX 600 10 TYPE which displays 16 bytes starting from HEX address 600 This will convert whatever is in these locations to ASC and output it which will display random characters and spaces until known data is placed in these locations Try it after first entering in string of data from the keyboard in RAM using the word EXPECT see Section 4 13 2 DECIMAL 600 40 CR EXPECT character string RETURN if less than 40 characters 600 40 CR TYPE Try it with a message of up to 40 characters Note that if the string is less than 40 characters whatever is in memory between the last entered character through the 40th character will be converted and displayed 4 12 5 Prepare to Output a String with COUNT Sometimes a string is stored as a length byte followed by the string itself and only the address of the string of the length byte is on the stack this is an alternate form for storing a string To conver
169. c fetch Fetches data b of bank n address addr b addr n MEMORY bank c store Stores data b in bank n address addr b addr nl n2 MEMORY bank e e c store Stores data b in bank nl address addr for n2 cycles Used in programming EEROM s and EPROM s BANKEX ECUT I addr n CONTROL BASE bank execute Execute FORTH word with CFA of addr in bank n Restore to current bank upon return addr NUMERIC base Leaves the address of the variable containing the current number base used for input and output conversion The range of BASE is 2 through 70 addr n compile time CONTROL begin Occurs in a colon definition in form BEGIN flag UNTIL BEGIN AGAIN BEGIN flag WHILE REPEAT At run time BEGIN marks the start of a word sequence for repetitive execution WORD Cont BL BLANKS BLK BLOCK STACK NOTATION DEFINITION GROUP ATTR A BEGIN UNTIL loop will be repeated until flag is true A BEGIN WHILE REPEAT loop will be repeated until flag is false The words after UNTIL or REPEAT will b xecuted when either loop is finished flag is always dropped after being tested The BEGIN AGAIN loop executes indefinitely
170. cabulary where the example definitions illustrated earlier in his manual were all placed and ASSEMBLER which contains definitions of 6500 instruction mnemonics mode symbols and other operations only used for 0 and 0 lt hich are defined in both vocabularies and used differently see Section 4 7 2 and 6 6 depending on which vocabulary is selected s Section 6 1 5 6 1 More on VLIST As mentioned at the beginning of Section 4 you can list the FORTH vocabulary by executing the word VLIST Press any key to terminate the VLIST VLIST can also be used to list the words contained in the assembler vocabulary see Section 6 Enter ASSEMBLER VLIST which will print the ASSEMBLER vocabulary and then link to the FORTH vocabulary and print that also The FORTH link word no name is shown at address 338 in the VLIST Then it is wise to execut FORTH to set the vocabulary back to FORTH Vocabularies ar object code has been compiled the dictionary and have no bearing on header ffectiv only at compile time less code they have no meaning after They only affect the search for names of words in
171. computer and the R65FR1 FORTH Development ROM as a teaching aid in order to learn the FORTH language and operation concepts If you already know the FORTH language you can probably skip certain sections and still use the language however it is recommended to review all sections to become familiar with the RSC FORTH mechanization and unique features Section 1 Introduction introduces the RSC FORTH language and the RSC FORTH User s Manual Section 2 Functional Description explains the hardware of the RSC FORTH system and how a RSC FORTH system can be constructed Section 3 FORTH Concepts provides a general overview into FORTH concepts and advantages This is a good chapter to read if you are new to FORTH Section 4 Elementary Operations leads you through elementary and common FORTH operations By following this section step by step you will learn how FORTH operates to a sufficient level to implement simple applications in FORTH 1 1 Section 5 Advanced Operations takes you into more complex FORTH operations once you have become familiar with the elementary FORTH operations described in Section 4 Section 6 Special Operations details the unique features of RSC FORTH not found in other FORTH systems designed to ease development in a single chip microcomputer system Section 7 RSC FORTH Assembler describes concepts and operating procedures associated with the RSC FORTH Assembler
172. computers The Rockwell R65F11 and R65F12 are complete high performance 8 bit NMOS single chip microcomputers and are compatible with all members of the R6500 family The R65F11 and R65F12 consist of an enhanced R6502 CPU an internal clock oscillator 3K bytes of masked Read Only Memory ROM 192 bytes of Random Access Memory RAM and versatile interface circuitry The interface circuitry includes two 16 bit programmable timer counters 16 bi directional input output lines including four edge sensitive lines and input latching on one 8 bit port a full duplex serial I O channel ten interrupts and bus expandability The innovative architecture and the demonstrated high performance of the R6502 CPU as well as instruction simplicity results in system cost effectiveness and a wide range of computational power These features in combination with the RSC FORTH high level operating system make the R65F11 and R65F12 ideal for microcomputer applications The R65F11 with its two 8 bit ports is housed in a 40 pin DIP For systems requiring additional I O ports the 64 pin QUIP version the R65F12 provides three additional 8 bit ports The kernel of the high level Rockwell Single Chip FORTH RSC FORTH language is contained in the preprogrammed ROM of the R65F11 and R65F12 RSC FORTH is based on the popular fig FORTH model with extensions All of the runtime functions of RSC FORTH
173. d n addr from t addr n addr n addr n addr b b addr addr n b addr b addr Same stack false Alias for UNTIL Alias for THEN Execute the definition with CFA of addr from bank n Return to current bank except that if top execute ELSE clause Replace word address by contents Store second word at address on top Fetch one byte only Store one byte only Print contents of address Add second number on stack to contents of address on top Move n bytes in memory Beginning at addr fill n bytes in memory with b Beginning at addr fill n bytes in memory with Zeroes Beginning at addr fill memory with blanks Exclusively OR byte at addr with byte b Program byte b into addr for n clock cycles Fetch one byte at addr from bank n Store one byte b at addr in bank n Program byte b into addr for nl clock cycles in bank n2 n bytes in Print number ASC string Output a carriage return and line feed to the serial line Type one space Type n spaces Print message terminated by Dump n bytes starting at address using current base Type string of n characters starting at address True if any key is depressed Read key put ASC value on stack Output ASC value from stack Read n characters or until carriage return from input to address Read the next text character string
174. d Internal Register Addresses Upper Laich B Cntr B Latch B CLA Flag Upper Latch B Latch C Latch B Lower Latch B Upper Latch A Cntr A Latch A CLR Flag Upper Latch A Lower Latch A Senal Transmitter Data Register Serial Comm Status Reg Bits 4 amp 5 only Serial Comm Control Register Interrupt Enable Register Clear int Flag Bits 0 3 only Write O s only NOTE R65F12 Only Addr 0014 0 Interval Timer 0 1 Pulse Generation 1 0 Event Counter Bus Mode Select 1 1 Pulse Width Meas 0 0 Interval Timer Q 1 Asymmetric Pulse Generation 1 0 Event Counter 1 1 Retriggerable Interval Timer Port B Latch 1 Enable Port D Tn State 0 Tri State gh Impedance Mode 1 1 Mux d Bus Mode Control Register EN CNA ENE dette fopet fe PAO Positive Edge Detect PA1 Positive Edge Detect PA2 Negative Edge Detect PA3 Negative Edge Detect Counter A Underfiow Flag Counter B Underfiow Flag IFR Addr 0011 IER Addr 0012 Figure 9 2 Register Bit Assignments 9 4 0 8 Bits Char 1 7 Bits Char 0 6 Bits Char 1 5 Bits Char 0 0 XMTR amp RCVR ASYN Mode 0 1 XMTR ASYN RCVR S R 1 X XMTR S R RCVR ASYN 0 RCVR Disable 1 RCVR Enable 0 XMTR Disable 1 XMTR Enable Serial Communications Control Register RCVR Data Reg Full RCVR Over Run Parity Error Frame Error Wake Up End of
175. d WHILE loops are provided all of these can be nested to any practical depth FORTH uses a STACK and its associated POSTFIX NOTATION also called Reverse Polish Notation RPN in which the operation codes are written after the operands which they use For example 242 in BASIC would be written 2 2 gt in FORTH Why does FORTH use a stack explicitly when most other languages hide their stacks from the user and avoid postfix in favor of more conventional notation Part of the answer is that the stac between subroutines FORTH reduces the whole language is built around return any number of arguments wit formal parameter or local variable The stack encourages extremely MODU great reliability Consider FORTH s word or procedure has only one ent communication with the outside worl effects on other modules variables each module is short commonly thre easier it is to test all paths thro FORTH is INTERACTIVE Testing is 1 k allows very low overhead for linking the cost of subroutines to very little and subroutine calls Routines Can accept and hout the complexity or other overhead of declarations LAR programming which can be debugged with programming environment Each module i e ry and one exit point Usually all d is through the stack so there are no side etc unless explicitly programmed Usually e to five lines The smaller a module is the
176. d n are used later for resolution of the offset and error testing WORD IFR STACK NOTATION DEFINITION GROUP ATTR MMEDIATE NDEX INTFLG NTVEC addr MISC interrupt flag register System address constant for addr of Interrupt Flag Register COMPILER immediate Marks the most recently made dictionary entry as a word which will b xecuted when encountered rather than being compiled addr INPUT OUTPUT U in Leaves the address of user variable containing the byte offset within the current input text buffer terminal or disk from which the next text will be accepted WORD uses and moves the value of IN nik Ae MASS index Lists the first lines of screens nl to n2 Terminates indexing if a key is typed ee MASS init Sets all locations in CYLINDER to SFF in effect forcing the next access to that drive to recalibrate from track O0 addr MISC interrupt flag System address constant for addr of High Level Interrupt Flag addr MISC interrupt vector System address constant for addr of High Level Interrupt Vector WORD ON DEFINIT STACK NOTAT ON GROUP ATTR NTERPRE ROVEC KHZ LATEST COMPILER interpret
177. d to by kernel following variables used in RO5FR1 Development ROM G 1 USER VARIABLES RAM MAP Continued Cold Warm Start Start Hex No Hex Hex Parameter Address Bytes Value Value Name Parameter Description 34A 34B 2 f ha CURRENT CURRENT vocabulary pointer 34C 34D 2 Um STATE Contains state of computation 34E 34F 2 ERU v m ESE Check Stack Pointer 350 351 2 So MODE Assembler addressing mode 352 353 2 A KHz Space for system clock frequency 354 37E 43 zy ues USERPAD User available less room for PAD 380 3FF 128 gt om ew av Terminal Input Buffer oo Ur iz 2 00 sF oy OT S wW H 0o ve MV Il Axe c HEX DEC ASC HEX DEC 00 0 NUL 20 32 01 1 SOH 21 33 02 2 STX 22 34 03 3 ETX 23 O 04 4 EOT 24 36 05 5 ENQ 25 1 06 6 ACK 26 38 07 7 BEL 27 39 08 8 BS 28 40 09 9 HT 29 41 OA 10 LF 2A 42 OB 11 VT 2B 43 OC 12 FF 2C 44 OD 13 CR 2D 45 OE 14 SO 2E 46 OF 15 SI 2F 47 10 16 DLE 30 48 11 17 DC1 31 49 12 18 DC2 32 50 13 19 DC3 33 51 14 20 DC4 34 52 135 21 NAK Juv 53
178. d to preserve the sign information since the numeric conversion itself requires a positive number hence th DABS The lt sets up the output conversion followed by the 4S sharp S which converts all digits of the number to ASCII The SIGN word then places an ASC minus sign if necessary it uses the extra copy of the high order part of the double precision number to detect if that number was originally negative The gt closes the conversion and leaves stack arguments set up for TYPE i e the number of characters to type on top of the stack and the address of the first one below it The SPACE word leaves one space after the number to Separate it from the next one 5 3 2 and HOLD Here is an example showing creation of a word D which prints a double precision number with decimal point and dollar sign Besides the above operations it also uses sharp which places a single digit into a string being created It also uses HOLD which takes an ASC value from the Stack and places that character into the number being formed Remember that the string builds from the least significant digits first The following colon definition shows how to convert digits individually placing additional characters such as decimal points and dollar signs where desired within a number DECIMAL DSs UD SWAP OVER DABS t 46 HOLD
179. d waits for them to come up to speed The active disk drive number is stored in DISKNO DISK calls SEEK after the appropriate drive is selected SEEK is passed to the number of the track which contains the data If the number for the current disk track stored in CYLINDER is out of range SEEK will recalibrate before trying to attain correct head positioning After the correct disk is selected and the head has been moved over the desired track DISK calls either DREAD if the Boolean value passed to it on the top of the stack is a one or DWRITE if it is a zero Both DREAD and DWRITE are passed the original memory address which was passed to DISK and the number of the 1K byte group of multiple sections to read Since there are 16 sectors per track that number will be zero through three The word NIT sets all disk drive track information in CYLINDER to SFF s in order to force recalibration if so chosen by the programmer An error on READ or WRITE will cause the displaying of an error message and return to the calling routine If more elaborate error handling or other mass storage techniques are desired it is up to the programmer to write his or her own versions of these primitives Control can be taken from these routines by modifying the vector in UR
180. defined by lt name gt WORD DO Cont DP ES gt DP DPL DRI STACK NOTATION DEFINITION GROUP ATTR O ES gt alters the code field and first parameter of he new word to execute the sequence of compiled ord addresses following DOES gt sed in combination with lt BUILDS he execution of the DOES gt part begins with the ddress of the first parameter of the new word amex gt on the stack Upon execution of lt name gt he sequence of words between DOES and will e executed with the address of lt namex gt s arameter field on the stack his allows interpretation using this area or its contents 3 HTOtCAMHGQETAY Typical uses include the FORTH assembler multi dimensional arrays and compiler generation 2 gt addr PARAMETER U d p Leaves the address of user variable the dictionary pointer which points to address the next free memory address above the dictionary The value may be read by HERE and altered by ALLOT addr PARAMETER d p slash Accesses user variable Addr is dictionary pointer for heads portion of definitions When normal code DP equals DP When headerless DP equals DP plus two addr FORMAT U d p 1 Leaves the address of user variable containing the number of digits to the right of the decimal on double integer input It may also be us
181. ding no interruption from the operator at that point the RSC FORTH System attempts to load a bootstrap program from floppy disk The first 128 bytes of Track 0 Sector 1 is loaded into RAM starting at address 005F After loading execution is turned over to the boot program at 005F The boot program can be any machine code program that will fit in 128 bytes Clever programmers will even be able to restart FORTH since it was a FORTH word that called the boot and execute a high level boot 2 2 5 Micro Monitor When the system issues the NO ROM message before actually calling the boot program the serial input channel is checked for a CNTL R character 12 Normally as the microcomputer powers up the contents of the serial input 25 AA ael AABB ENTRY POINT ROUTINE C coop xxoe sl HHLL PFA OF WORD TO EXECUTE HHH HHL 20004 AS AS ES AUTO START ROM PATTERN cy AUTO START PATTERN 1K BOUNDARY 1K BOUNDARY AUTO START FORTH PROGRAM AUTO START MACHINE CODE PROGRAM Figure 2 3 Auto Start ROM Code Example register will be some other value thus boot from floppy disk will be initiated If a CNTL R key combination is received from the serial input channel then RESET pressed a program called the Micro Monitor is entered The Micro Monitor is completely self contained in the kernel The microcomputer with the kernel requires only RAM from address 0300 through 3FF to run the Micro Monito
182. e kernel Therefore even though CASE is not in the kernel words defined with CASE can be used in standalone target compiled systems without the support of the Development ROM 6 3 TARGET COMPILATION DICTIONARY CONTROL Although FORTH code by its very nature is compact it is often desirable to compress code even further by target compilation The process of target compilation in operation usually from FORTH so program Th 2K to 5K bytes itself is so More advanced target compiling systems These programs generat by the application dictionary urce code on disk screens large the resultan a new kernel th the order of 2K bytes for a simple program complicated and takes more memory in th to compile conventional FORTH systems usually implies a disk to disk e compiling program supplies a runtime kernel FORTH structures are then compiled onto the kernel Since the operating target compilation t program generally is assembled on disk of fixed size are not limited to fixed size kernels at contains onl The finished program is usually much smaller ly the functions required on The compil ing program is much more e compiling system and a much longer time 6 3 1 Headerless Code Generation The RSC FORTH system has an advanced method of FORTH target compilation You have the option when your code is entered of selecting either in line dictionary code or
183. e also initialized to their default values If a warm start is detected only TIB RO and SO are reset to default values The meanings of these variables are described in Appendix A 2 2 2 Application Program Auto Start Whether a warm or cold reset the memory map is then examined at every 1K byte boundary starting at location 0400 i e 0400 0500 0600 etc through S3F00 The first two bytes at each boundary are compared to an A55A bit pattern This pattern indicates an auto start ROM is installed If the auto start pattern is present the next two bytes must point to the Parameter Field of a high level RSC FORTH word to be executed upon reset Assembly language routines can also be autostarted by using a series of indirect pointers Details on auto start ROM patterns are shown in Figure 2 3 2 2 3 Development ROM Startup The R65FR1 Development ROM is an example of an auto start ROM If there is no other auto start pattern lower in the memory map when the operating system finds the R65FR1 Development ROM the familiar start up of the RSC FORTH will occur and the message RSC FORTH VI 5 is displayed FORTH words can now be entered interactively see Section 3 1 2 2 4 Bootstrap Program Load If no development ROM is found the message NO ROM is issued by the operating system Provi
184. e can then control the assembly time security checks as follows First we must note the parameters utilized by the control structures at assembly time The notation below is taken from the assembler glossary in Appendix D The indicates assembly time execution and separates input stack values from the output stack values BEGIN gt addrB 1 UNTIL S addrB cc AGAIN addrB 1 WHILE gt addrB 1 addrB 1 addrW 3 REPEAT addrB 1 addrW 3 IF gt SOC addrI 2 ELSE gt addrI 2 addrE 2 THEN gt addrI 2 or addrE 2 Where the address values indicate the machine location of the corresponding B EGIN I F or E LSE and cc represents the condition code to select the processor status bit referenced The digit 1 2 or 3 is tested for conditional pairing The general method of security control is to drop off the check digit and manipulate the addresses at assembly time The security against errors is less but the programmer is usually paying intense attention to detail during this effort 7 9 ADDING ASSEMBLY CODE TO A DEFINING WORD I The word CODE is used in a colon definition to stop compiling and to add assembly code to the definition The format is as follows name FORTH words CODE assembl
185. e error checking DICTIONARY altot Adds the signed number to the dictionary pointer DP May be used to reserve dictionary space or re origin memory n is the number of bytes pr gt DICTIONARY allot slash Adds the signed number to the dictionary pointer DP May be used to reserve space in the heads dictionary or re origin memory ni A2 m3 ARITHMETIC W and Leaves the bit wise logical AND of nl and n2 as n3 VOCABULARY assembler Sets the vocabulary to ASSEMBLER addr DICTIONARY autostart Establishes autostart pattern of memory location addr Bit pattern A55A is put at addr Parameter Field Address CFA 2 is placed at addr 2 MASS bytes per buffer Leaves the number of bytes value 1024 per data buffer the byte count read from mass storage by BLOCK The actual buffer size is four bytes larger than this value addr MASS blocks per side User variable containing number of 1K byte blocks per side per disk drive WORD B SCR BANKC BANKC BANKEEC STACK NOTATION DEFINITION GROUP ATTR n MASS blocks per screen Leaves the number of blocks value 1 per FORTH screen By convention an editing screen is 1024 bytes organized as 16 lines of 64 characters each addr n b MEMORY bank
186. e for th to decimal and later restore DECIMAL converts the If you need to check the base often you can define do it such as BASE BASE DUP DECIMAL BASE DUP duplicates the base I O number conversion base prints the base and removes it from the stack a colon definition word to When a colon definition is compiled the base in effect at compile time is the one that counts Notice that the following code is erroneous and fails to compile DECIMAL MASK HEX OOFF OR OO0FF The OOFF is un HEX does not recognized because the base is decimal at compile time the word change the base immediately as was intended but compiles as part of the definition of MASK It will change th executed The correct code is base when MASK was HEX MASK OOFF OR DECIMAL A possible source of confusion is the fact that in binary the numbers 2 3 and 4 as well as 0 and 1 are correctly recognized on input This happens because the numbers 0 4 are so commonly used that they were made into constants to save memory space Since these common numbers are FORTH words in the dictionary they are recognized regardless of the number base in effect 4 12 OUTPUT WORDS 4 12 1 Print Right Justified with R We have already seen the word dot used for printing numbers Other operators are available to
187. e locators of the present input stream from IN and BLK If interpretation is not terminated explicitly it will be terminated when the input stream is exhausted Control then returns to the input stream containing LOAD determined by the input stream locators IN and BLK addr n compiling CONTROL TG VIoOop Occurs in a colon definition in form DO LOOP At run time LOOP selectively controls branching back to the corresponding DO based on the loop index and limit The loop index is incremented by one and compared to the limit The branch back to DO occurs until the index equals or exceeds the limit at that time the parameters are discarded and execution continues ahead At compile time LOOP compiles LOOP and uses addr to calculate an offset to DO n is used for error testing nl n2 d ARITHMETIC m times A mixed magnitude math operation which leaves the double number signed product of two signed number dnl n2 n3 ARITHMETIC m divides A mixed magnitude math operator which leaves the signed remainder n2 and signed quotient n3 from a double number dividend d and divisor nl The remainder takes its sign from the dividend udl u2 u3 ud4 ARITHMETIC m divide mod An unsigned mixed magnitude math operation which leaves a double quotient ud4 and remainder u3 from a double dividend udl and single divisor u2
188. e redefined ven the system words such as DO itself Any further use of the word will refer to the latest definition but all earlier uses still refer to the definition which was in effect when th arlier references were compiled Execute SERIES now SERIES OLLE 2 3 4 5 00 48 9 TO Dh T2 ES X4 15 6 17 18 19 OK In the examples above notice that the only difference between SERIES and NSERIES is that the latter does not place a loop terminating value on the Stack Instead it uses whatever was on the stack when NSERIES was executed The NSERIES example also shows that the arguments to DO the loop initial and terminating values need not be literal numbers instead they can be computed or obtained in any way DO doesn t care how its arguments got onto the Stack This feature helps keep FORTH code modular and reduces side effects when changes are made DO LOOP and the other control structures which will be introduced later can only be used inside colon definitions i e they cannot be executed directly as commands at the terminal DO and LOOP are in a special class of words called immediate words These are not compiled like other words used in colon definitions but instead they execute at compile time to handle special compilation functions e g to compile an internal branch back from the LOOP to
189. ed hold output column location of a decimal point in user generated formatting The default value on single number input is 1 addr n m MASS d read Reads from disk sector 4n 1 to memory location addr in 1K byte records and leaves the disk error byte on the stack see E 4 t WORD DROP DUMP DUP DWR ELSE STACK NOTATION DEFINITION GROUP ATTR uet STACK drop Drops the number on top of the stack from the stack addr n INPUT OUTPUT dump Displays the contents of n memory locations beginning at addr Both addresses and contents are shown in the current numeric base DUMP outputs 8 bytes on a line Iced STACK dup Duplicates the value on the stack addr n MASS d write Writes to disk sector 4n 1 from memory location addr in 1K byte records and leaves the disk error byte on the stack see E 4 E b addr n MEMORY e e c store Stores data b in addr for n clock cycles Used for EEROM or EPROM programming CONTROL Eee addrl nl addr2 n2 compiling else Occurs within a colon definition in the form IF ELSE THEN At run time ELSE executes after the true part following IF ELSE forces execution to skip over the following false part and resumes execution after the THEN It has no stack
190. eed program development time If FORTH is not fast enough for some purposes a powerful technique is to first develop the program logic in high level FORTH and test the logic at reduced speed When it works correctly code in assembly language only those FORTH words that are required to bring the speed performance to the desired level By this technique program development time is reduced to the minimum 8 3 3 Example An example of an interpretive interrupt handler is shown in Figure J 2 Only two short CODE definition words are defined one to set the request bit in INTFLG when an IRQ interrupt occurs due to Timer 3 timeout and one to clear the inhibit bit in INTFLG when the interpretive interrupt word completes execution The changes to the 24 Hour Clock to use interpretive interrupts involve replacing the code interrupt handling routine with a colon definition or code fragment service word writing the interpretive interrupt arm and trigger words and then the FORTH interrupt processing word The conventional interrupt handler from PHA to RTI is replaced with two smaller code routines one a code fragment and the other the ARM word that goes at the end of the FORTH interrupt processing word The code fragment is the interrupt service subroutine that is executed with each IRQ interrupt It sets the interrupt request bit in INTFLG and clears the Timer s IRQ request bit wh
191. effect At compile time ELSE emplaces BRANCH reserving a branch offset leaves the address addr2 and n2 for error testing ELSE also resolves the pending forward branch from IF by calculating the offset from addrl to HERE and storing at addrl See IF and THEN WORD EMPTY BUFF ENCLOSI LH ENDIF ERASE STACK NOTATION DEFINITION GROUP ATTR char INPUT OUTPUT emit Transmits an ASC character to the selected output device See KE RS MASS empty buffers Marks all block buffers as empty not necessarily affecting the contents Updated blocks are not written to the mass storage This is also the required initialization procedure before first use of the mass storage PRIMITIVE addr char addr nl n2 n3 enclose he text scanning primitive used by WORD rom the text address addr and an ASC delimiting haracter is determined the byte offset to the irst non delimiter character nl the offset to he first delimiter after the text n2 and the ffset to the first character not included n3 his procedure will not process past an ASC null treating it as an unconditional delimiter HO ctro hd CONTROL I8 end This is an alias or duplicate definition for UNTIL addr n co
192. efine a new word to use MULTIPLY CR ANSWER 5 RETURN OK and test it ECIMAL 108 MULTIPLY ANSWER 540 OK 1345 MULTIPLY ANSWER 6725 OK ES 4 4 4 Commenting Because the inputs and outputs are not explicit in FORTH code it is very important to show them in the documentation It is recommended that they be included as comments in the code and also in a separate glossary of operations Each glossary entry should include the inputs outputs and a short description of what the operation does usually two or thr Sentences ar nough Comments in FORTH are enclosed in parentheses A space must follow the left parenthesis because the left parenthesis is itself a FORTH word which causes FORTH to look for a closing delimiter The closing right parenthesis need not be preceded by a space however since it is a delimiter and not an operation 4 19 A RETURN also acts like a right parenthesis to terminate a comment FORTH comments can be included on as many lines as needed however the comment must start with a left parenthesis followed by a space on each new line A conventional form of comment first lists the inputs then three dashes then the outputs A period may be used to separate the last output word from the words of any description of the function of the operation Therefore the TEST OP definition could look like TEST OP N MULT BY 5 AN
193. egister SCSR If enabled an IRQ will be generated whenever any of these bits SCSRO SCSR3 are true Serial words received are available in the Serial Channel Data Register SCDR by character fetch Words can be transmitted by character storing bytes in the SCDR when the status flags indicate transmitter data register empty 9 3 COUNTER TIMERS The R65F11 R65F12 Microcomputers contain two 16 bit counter timers and three 16 bit latches Each of the two counters A and B can be independently programmed to operate in one of four selectable modes Counter A supports an Interval Timer Event Counter Pulse Width Measurement and Pulse Generation Mode Counter B has an Internal Timer Event Counter Retriggerable Interval Timer and Asynchronous Pulse Generation Mode The operating modes of the counter timers are controlled by the Mode Control Register MCR All counting begins at the initialized values and decrements from there When modes are selected requiring a counter input output line PAZ is automatically selected for Counter A and PA5 for Counter B 9 3 1 Counter A Counter A consists of a 16 bit counter and a 16 bit latch organized as follows Lower Counter A LCA Upper Counter A UCA Lower Latch A LLA and Upper Latch A ULA The counter contains the count of either 02 clock pulses or external events depending on the counter mode selected The contents of Counter A ma
194. eld address NFA c LFA converts the PFAPTR into the link field address LFA d CFA converts the PFAPTR into the code field address CFA e PFAPTR converts the name field address NFA to the parameter field pointer address 5 5 3 FORTH Word Handling Examples To print the contents of LFA of CLIT perform HEX CLIT LFA 0 CR D 202C To print the name of LIT perform LIT NFA COUNT 1F AND CR TYPI BLEF GI To print the topmost word name in the dictionary perform LATEST CR 1D TASK A simple list of all words in the FORTH dictionary can be obtained with IR CR LATEST EGIN UP ID CR FAPTR LFA DUP UNTIL OK R lt RETURN gt IR TASK S Press RESET to terminate list ovUWD UU 5 6 VOCABULARIES Vocabularies are groupings of FORTH words They are used to allow the same names to be used for different operations in different application areas If a name is redefined in the same vocabulary only the latest definition will be accessible But if the same name is used in two or more different vocabularies definitions can be selected he RSC FORTH system as supplied includes two vocabularies FORTH he assembler S Section 6 For example RSC FORTH has two words z DO all the which is he default vo
195. en the dictionary is still present thorough testing is possible The code is however in final format and requires no changes before storage in PROM or ROM The option of using the target compilation features is totally at the discretion of the user Either way after target compilation is set up there is no detectable difference in the operation of the RSC FORTH system There are basically three reasons to choose target compilation The most obvious is to save room in the target storage ROM Another desirable feature is that target compilation provides an immediate level of program security Only the most sophisticated program pirates will be able to reconstruct program flow without ven then there will be a severe penalty in time required to decompile the target code Final compiling some words and normally compiling others created Other languages can even be written in FORTH the dictionary header information and The programmer has complete control over t variable called HEADERL ESS contains a he state o ntered ar ither normal or target compiled When codes with heads are generated When in one memory area controlled by DP reference to DP 6 3 2 Target Compilation with H C Normally direct reference to H initiates th ntire target compilation process H C HEADERLESS and takes on user s HEADS XXXX on one lin
196. ending CNTL R then pressing RESET without an auto start ROM in the system or by commanding MON in the development system gt N1111 The gt indicates the Micro Monitor is ready for input The N1111 entered by the operator puts a 1111 on the data stack gt N222 The Micro Monitor returns the gt after the last command is finished The operator enters the second number 0222 gt WE 778 The W entered by the operator indicates the following number is a FORTH word to be exe cuted The address F778 is the Parameter Field Address of the FORTH word The Micro Monitor causes the two numbers to be added therefore and the result left on the gt WE T EA 1333 The operator enters another FORTH word to be executed This one is the command which outputs the top value from the data stack The outputted result is displayed on the same line After command completion the Micro Monitor displays the to indicate that it is ready for another input A list of all the available FORTH words available in the kernel with their Parameter Field Addresses are listed in Table 2 1 There are many useful words that can be accessed by the user with the Micro Monitor It is possible to examine I O ports load programs from disk and even program EPROMs under direction of the Micro Monitor It should be easy to imagine many uses for the Micro
197. ent of a double precision number WORD DO DO GI STACK NOTATION DEFINITION GROUP ATTR nl n2 run time CONTROL addr n compile time Occurs in a colon definition in form DO LOOP DO vs HOOR At run time DO begins a sequence with repetitive execution controlled by a loop limit n1 and an index with initial value n2 DO removes these from the Stack Upon reaching LOOP the index is incremented by one At the LOOP the index is modified by a positive or negative value Until the new index equals or exceeds the limit execution loops back to just after DO otherwise the loop parameters are discarded and execution continues ahead Both n1 and n2 are determined at run time and may be the result of other operations Loops may be nested Within a loop I will copy the current value of the index to the stack See I LOOP LOOP LEAVE At compile time within the colon definition DO compiles DO and leaves the following addr and n for later error checking DEFINING does Defines the run time action within a high level defining word Used in the form lt name gt BUILDS DOES 56 and then lt name gt lt namex gt Marks the termination of the defining part of the defining word lt name gt and begins the definition of the run time action for words that will later be
198. er the other starting with LIT to TASK followed by all user created words Each word is composed of six sections flag bits and name character count name link address parameter field pointer code address parameter field Here is a picture of the dictionary with a word expanded with its sections LIT WORD WORD WORD WORD WORD E E TASK COUNT NAME LINK PFAPTR CODE PARAMETER pec Rh onn NFA LFA PFAPTR CFA PFA The first byte of a word begins with the name field and contains the number of characters in the word s name along with two flag bits 1 xX X X X X X x character count smudge flag precedence flag The MSB is set to indicate the start of a name The precedence flag indicates if the word is for compile or immediate execution The smudge flag prevents the word from being found in the dictionary during compilation If the compilation finishes successfully the smudge bit is reset to zero allowing the name to be recognized SMUDGED words will show up in a VLIST however To eliminate a SMUDGED word from the dictionary toggle the SMUDGE bit by using the word SMU The the The the DGE and then use FORGET to eliminate the word from the dictionary name field continues with the ASC characters of the name with the MSB of last character set to indicate the end of the name link address is the address of the count byte of the
199. erations which let you define your own numeric formats 5 3 1 S D t S SIGN and 4d To use these operations first get a double precision number on the stack Then a special operation lt less sharp starts numeric conversion Digits are converted from the right i e least significant digit first ASC characters such as decimal points and dollar signs can be added where needed Then another special operation gt sharp greater closes the conversion Between the lt and the gt a double precision number from the stack is converted into a string of ASC characters representing the number s value Depending on the program this conversion can be done a character at a time or several characters at once The least significant digit is converted first and builds in memory starting at PAD and moving down as the string grows For example the following definition creates and tests a word PRINT which works like the print command This example illustrates a fairly simple case with no added character PRINT S D SWAP OVER DABS ft S SIGN gt IYPE SPACE Enter a number to test PRINT 12345 PRINT RETURN 12345 First S gt D converts the top stack number to double precision The SWAP OVER in effect makes an extra copy of the high order 16 bit part below the double precision number of the stack this is require
200. erpreter executes from the assembly time stack value to this FORTH address as the As of erpreter named one definition to the next return control to NEXT NEXT This short code routine moves execution from At the end of your CODE definition you must or else to other code which returns to NEXT T is a constant that specifies the machine address of FORTH s JMP NEXT at F428 Here NEXT it assembles a machine code last instruction is the operand for JMP jump to the address If control is not returned in the CODE definition improper operation of the microcomputer and possible alteration of your program may result d The the END CODE word terminates the CODI name CURRENT It also exits the E definition with a SMUDGE of ASSEMBLER making The object code of our example is 84 45 00 14 E6 4C 58 49 D4 08 08 00 6F CO 7 2 ASSEMBLER OP CODI The bulk CONTEXT the same as Name letter count with MSB set POPA Name with MSB of 1 link field code field INC PORTA location 00 JMP NEXT ast digit set of the assembler consists of dictionary entries for the R6500 mnemonic op codes Refer to Appendix code that is generated by each mnemonic op code 7 4 B in the R6500 Programming Manual to see the machine 7
201. esentations FFFF and 1 are the same in 16 bit 2 s complement arithmetic With the operations AND OR and XOR any truth value functions of one two or more arguments can be used 4 8 4 BEGIN Loops In a BEGIN UNTIL loop the UNTIL takes a Boolean value from the stack If false it loops back to the BEGIN if true it terminates the loop i e the loop continues UNTIL a condition is true The following loop executes until HOT is true non zero BEGIN PERFORM AN ACTION 2HOT STOP IF HOT UNTIL The BEGIN WHILE REPEAT loop is almost opposite it will continue to execute the statement s between WHILE and REPEAT while the condition between BEGIN and WHILE is true WHILE tests the Boolean if true it does nothing allowing control to remain in the BEGIN REPEAT loop if false it branches out of the loop to beyond the REPEAT The REPEAT always branches back to the BEGIN The following loop is almost the same as the UNTIL loop above BEGIN HOT 0 WHILE PERFORM AN ACTION REPEAT The difference is that the words contained between WHILE and REPEAT loop can execute zero
202. ess of the FORTH dictionary using HERE and the starting address of the temporary storage area using PAD COLD RSC FORTH V1 6 PAD HERE HEX S 411 37E OK In most FORTH systems PAD Starts 68 bytes above the start of the FORTH dictionary To make RSC FORTH compatible with other FORTH systems define PAD as follows DECIMAL PAD HERE 68 Since PAD is located relative to the current top of the RAM dictionary it will change when any new words are defined or when words already in the dictionary are forgotten Usually this is not a problem because any particular test or run would move data into its temporary storage at PAD and not rely on data stored there previously As an example add a word to the FORTH dictionary that can be used to check where HERE and PAD are located as other words are either added or deleted from the dictionary Then use it first to check itself CK PAD CHECK PAD amp HERE PAD HERE HEX CR HERE CR PAD Enter CK PAD and compare the results CK PAD HERE 43D PAD 481 OK Now the memory fetch and store words can be tested using PAD as available memory Try the sequence DECIMAL OK PAD 20 BLANKS OK 15 PAD OK 15 PAD 10 C OK PAD 10 HEX DUMP XXX F 020202020 2020 20 20 F 20 20 20 20 20 OK
203. ext ASC character placed in an output string from udl Result ud2 is the quotient after division by BASE and is maintained for further processing Use between t and 4 See S d addr n FORMAT sharp greater Terminates numeric output conversion by dropping d leaving the text address and character count n suitable for TYPE ud 0 0 FORMAT sharp s Converts all digits of a ud adding each to the pictured numeric output text until the remainder is zero A single zero is added to the output string if the number was initially zero Use only between 4 and gt addr DICTIONARY ck Used in the form name If executing leaves the parameter field address of the next word accepted from the input stream If compiling compiles this address as a literal later execution will place this value on the stack If the word is not found after a search of CONTEXT and FORTH vocabularies an error message is displayed B 3 WORD CODI GI LOOP ABORT STACK NOTATION DEFINITION GROUP ATTR MISC paren Used in the form CECE Accepts and ignores comment characters from the input stream until the next right parenthesis As a word the left parenthesis must be followed by one blank It may be freely used while executing or compiling An error condition exists if the input stream is exhausted be
204. f memory starting at the second address Try 200 40 80 FILL OK 240 40 FF FILL OK 200 280 8 CMOVE OK 240 288 8 CMOVE OK 280 10 DUMP 280 80 80 80 80 80 80 80 80 FF FF FF FF FF FF FF FE OK 4 16 CMOVE works from the left to right so be careful if the from and to memory areas overlap 4 4 DEFINING YOUR OWN OPERATIONS FORTH allows you to create your own operations These new FORTH words become an integral part of the language just like those which are pre defined in RSC FORTH Your new words can take any number of arguments from the stack and return any number of results The names of your operations can have up to 31 characters They can use any ASC characters except blank delete null and carriage return For instance an operation name could be a number or even be non displaying or non printing control characters although such names are discouraged Even names already used by the system may be redefined as something else therefore there is no reserved word list in FORTH When a name is redefined the old definition becomes inaccessible for later use in the program although all earlier references to that name will remain as before So do not redefine a name if you want to use the old definition later Names which are descriptive of the function they perform make the cod asier to read Good choice of names is important for later use of the code especially by
205. ffset in current input stream 312 313 2 EL Zo e DPL Number of decimals in double precision input 314 315 2 im ET HLD Address of current output 316 317 2 m Lus qm DISKNO Number of selected disk drive 318 31B 4 FF FF CYLINDER Track of each disk EEEE 31C 31D 2 80 c B SIDE Blocks per side per disk 31E 31F 2 F8 17 em UFIRST Start of mass storage buffer 320 321 2 00 20 gt Sw ULIMIT End of mass storage buffer 322 323 2 00 00 OFFSET Block offset to disk drives 324 325 2 31 00 A D WIDTH Number of letters in name 326 327 2 00 00 WARNING Error message action switch 328 329 2 04 04 FENCE Forget protection point 32A 32B 2 die oS DP Dictionary pointer 32C 32D 2 00 00 pP Dictionary pointer for heads when headerless 32E 32F 2 00 00 eS HEADERLESS Headerless code flag 330 331 2 3C 03 VOC LINK Last VOC field 392 333 2 81 AO 5 FORTH chain head 334 335 2 04 04 Sz X FORTH vocabulary pointer 336 337 2 00 00 AI FORTH vocabulary link 338 339 2 81 AO E ASSEMBLER chain head 33A 33B 2 36 03 A ASSEMBLER vocabulary pointer 33C 33D 2 00 00 me em ASSEMBLER vocabulary link 33E 33F 2 5G 3 gt 5 UABORT CFA of UABORT orphan word 340 341 2 zx E USE Mass storage buffer to use 342 343 2 xx zx PREV Mass storage buffer just used 344 345 2 ue ts BLK Number of current blk 346 347 2 S ve SCR Most recently listed screen 348 349 2 os CONTEXT CONTEXT vocabulary pointer Last address referre
206. fication directly The word is gt LINE pronounced to line To use gt LINE first list a screen this has the same meaning as showing a block Any line on that screen can be replaced by typing the line number and gt LINE followed by a carriage return LINE then accepts up to 64 characters from the terminal and places them on the screen at the specified line 6 5 3 Dumping a Memory Block A pair of high and low level utility words are ADMP and DUMP ADMP causes the system to dump the contents of a memory block in a standard format to the System terminal Data can be transferred to one of several commercially available PROM programmers for permanent storage In this format every record begins with a semicolon followed by a two ASC character representation of the number of bytes in hex in this record Next is the four ASC character number starting address in hex for this record The individual bytes follow each byte represented in the form of two ASC characters as the hex value A 16 bit checksum is sent as the final field with four digits in hex Multiple records are sent until all of the memory designated is dumped A final record is sent WwW E K ith zeros for the number of bytes in hex and address and a final total 16 bit hecksum in hex This is the same format used by the AIM 65 AI
207. field of the FORTH word being executed Leaves the address of a temporary buffer for saving the X register 8 M SCELLANEOUS tz ND CODE A T Er Marks the end of a CODI definition E to direct memory Sets MODE addressing on z page APPENDIX D RSC FORTH ASSEMBLER GLOSSARY This glossary contains the definitions of all words in the RSC FORTH ASSEMBLER vocabulary with exception of the op codes The definitions are presented in ASC sort order Stack Notation The first line of each entry shows a symbolic description of the action of the procedure on the parameter stack The symbols on the left indicate the order in which input parameters have been placed on the stack Three dashes indicate the execution point any parameters left on the stack after execution are listed on the right In this notation the top of the stack is to the right Symbol Definition addr addrl memory address GG OCLl s condition code Dade 16 bit signed number Pronunciation The natural language pronunciation of FORTH names is given in double quotes Capitalization Word names as used within the glossary are conventionally written in upper case characters Lower case is used when reference is made to the run time machine codes not directly accessible e g VARIABLE is the user word to create a variab
208. fines a word INPUT which when executed accepts a number returning the address just beyond the number and the number itself in double precision form as two numbers on the stack NUMBER will not skip leading blanks or handle minus signs you must do so if necessary By defining INPUT you have handled the difficult part of NUMBER just once Subsequent inputs can be processed easily by using the INPUT word 5 4 6 Input a Number with NUMBER The word NUMBER written without the parentheses will handle leading blanks and the minus sign But if the string being converted is in error e g contains alphabetic letters FORTH will handle the error itself by echoing the unrecognized string with a question mark the user cannot get control to process the error differently Therefore the more primitive NUMBER is usually preferred for turnkey applications 5 5 DICTIONARY STRUCTURI GI As you are well aware by now FORTH consists primarily of a dictionary of words The FORTH words were listed using VLIST in Section 4 and are shown in Table 4 1 This section describes the structure of the words in the dictionary RSC FORTH allows some very useful ways to manipulate the dictionary not found in other FORTH systems These unique features are discussed in Section 6 5 5 1 FORTH Word Structure The FORTH words are arranged one aft
209. for the Lower read at location 001C also clears the Counter B Underflow Flag ins the counter initialization value and can be loaded at any time a write to the Upper Latch B at location 001D and the Lower Latch B 01C In each case the contents of the accumulator are copied into the applicabl Counter B can contents of t the 16 bit La latch value a IFR5 may be c to address lo Counter A in e latch register be initialized at any time by writing to address 001E The he accumulator is copied into the Upper Latch B before the value in tch B is transferred to Counter B Counter B is also be set to the nd the Counter B Underflow Flag bit IFR5 is set to a 1 whenever Counter B underflows below 0000 leared by reading the Lower Counter B at location 001C by writing cation 001E or by RES Counter B operates in the same manner as the Interval Timer and Event Counter modes The Pulse Width Measurement Mode is replaced by the Retriggerable Interval Timer mode and the Pulse Generat a Retri ion mode is replaced by the Asymmetrical Pulse Generation Mode ggerable Interval Timer Mode When operating in the Retriggerable Interval Timer mode Counter B is e initialized to the latch value by writing to address 001E by a Counter B underflow or whenever a positive edge occurs on the CB pin PA5 The Coun
210. fore the right parenthesis PRIMITIVE The run time procedure compiled by which transmits the following in line text to the selected output device See PRIMITIVE The run time procedure compiled by CODE that rewrites the code field of the most recently defined word to point to the following machine code sequenc See CODE PRIMITIVE The run time procedure compiled by LOOP which increments the loop index by n and tests for loop completion See LOOP PRIMITIVE Executes after an error when WARNING is 1 This word normally executes ABORT but may be altered with care to a user s alternative procedure See ABORT limit 1 start PRIMITIVE The run time procedure compiled by DO which moves the loop control parameters to the return stack See DO B 4 WORD LOOP NUMBE rj W ay STACK NOTATION DEFINITION GROUP ATTR PRIMITIVE addrl addr2 pfa byte tf ok addrl addr2 ff bad Searches the dictionary starting at the name field address addr2 matching to the text at addrl Returns parameter field address length of name field byte and Boolean true for a good match If no match is found only a Boolean false is left See FIND nl n2 addr count PRIMITIVE
211. g debugging programs and learning FORTH Dl m gt ms ARITHMETIC divide Divides nl by n2 and leave the quotient n3 n3 is rounded toward zero The remainder is lost nl n2 n3 n4 ARITHMETIC divide mod Divides nl by n2 and leaves the quotient n4 and remainder n3 n3 has the same sign as nl cce i NUMERIC zero The number zero is placed on top of the stack n flag COMPARISON zero less Leaves a true flag 1 if the number is less than zero negative otherwise leaves a false flag 0 The number is lost nes flag COMPARISON zero equals Leaves a true flag 1 if the number is equal to zero otherwise leaves a false flag 0 The number is lost WORD OBRANCH 1 2 2DROP STACK NOTAT ON DEFIN GROUP ATTR flag zero branch PRIMITIVE The run time procedure to conditionally branch If the flag is false zero the following in line parameter is added to branch ahead or back Compiled by IF one UNTI the interpretive pointer to and WHILE Lo NUMERIC The number one is placed on top of the stack n ntl one plus A n1 one minus ARITHMETIC Increments n by one according to the operation of ARITHMETIC Decrements n by one according to
212. gt 1 The word MOD divide mod leaves both the quotient top of the stack and the remainder second on the stack for example 22 7 MOD CR 31 5 1 2 Absolute ABS and Negate NEGATE To get the absolute value of a number use the word ABS For example take the absolute values of both a positive and a negative number 22 ABS lt RETURN gt 22 22 ABS RETURN 22 To reverse the sign of a number use the word NEGATE Negate both a positive and a negative word for example 33 NEGATE RETURN 33 33 NEGATE RETURN 33 5 1 3 Simple Increment and Decrement 1 2 que 2 Four words are included for convenience of incrementing or decrementing a value on the stack by one or by two They are 1 one plus Increment by 1 2 two plus Increment by 2 1 one minus Decrement by 1 2 two minus Decrement by 2 Try the following examples 1 1 RETURN 2 2 2t RETURN 4 3 1 RETURN 2 5 2 RETURN 3 5 1 4 Minimum MIN and Maximum MAX When you wish to limit the range of number between a lower and upper value the words MAX and MIN will compare the values of the top two numbers on the stack and leave only the greater or smaller number respectively 2 MIN RETURN 1 10 5 MIN RETURN 10 4 7 MAX RETU 10 5 MAX lt RETU RN gt 7 RN g
213. h it Note that a minus number on top always changes the sign of the double precision number below Note also that the single precision number is removed by the D operation 56789 78 D D RETURN 56789 5 2 4 Unsigned Compare U lt Addition and subtraction are the same for signed or unsigned single precision numbers so there are no special operations for these Comparison is different however so an unsigned compare word U lt u less than should be used instead of the signed compare word Using in a comparison where one number exceeds 32 767 will result in an incorrect answer The comparison 20000 40000 RETURN O gives 0 Boolean false because 40 000 as a signed 16 bit number is negative and is therefore less than 20 000 The comparison 20000 40000 U lt RETURN 1 yields 1 Boolean true which is the correct result Use U to compare addresses unless you are sure both of them will be below 32 768 or both above t 5 2 5 Unsigned Multiply U and Divide U Two other unsigned operations are provided The unsigned multiply word U u times multiplies two unsigned single precision numbers to give an unsigned double precision number For example 40000 40000 U CR D 1600000000 The unsigned divide word U u divide divides an unsigned double precision number second on stack by an unsigned single precision number top of stack to give an unsigned
214. had little effect start and check the FORTH dictionary 5 6 3 Use LATEST and HERE to Check Directory Addresses The word LATEST leaves on the stack the name field address of the last word pointed to by CURRENT Do a COLD HEX LATEST lt RETURN gt 404 The word HERE leaves on the stack the next available dictionary address where new words can be added HERE RETURN 411 ASSEMBLER Vocabulary link FORTH _ Vocabulary C HERE LATEST 5 6 4 Application Libraries You can create your own vocabularies in order to keep different application libraries separate from each other Just execute VOCABULARY lt name gt where lt name gt is the name up to 31 characters you want the new vocabulary to have Then you would usually say lt name gt DEFINITIONS and begin putting your application library words into the lt name gt vocabulary In the RSC FORTH system the new vocabulary will be linked to whatever vocabulary it was created in usually FORTH All vocabularies form a tree allowing sub vocabularies nested to any depth All vocabularies from CONTEXT along the branching path back to the root of the tree which is always FORTH will be searched whenever a name is entered into the FORTH system for execution or compilation To create a new vocabulary use the word VOCABULARY along with the vocabulary name to
215. he ASSEMBLER vocabulary are defined in Appendix D RSC FORTH Assembler Glossary in ASC sort order To examine the assembler words perform a cold start command ASSEMBLER and run a VLIST The Assembler VLIST is shown in Figure 7 1 Note that the ASSEMBLER VLIST continues into the FORTH vocabulary upon completion of the ASSEMBLER word list Press any key to terminate the VLIST before completion Code assembly consists of interpreting entered words with the ASSEMBLER vocabulary as CONTEXT see Section 5 6 2 Thus each word in the input stream is matched according to the FORTH practice of searching CONTEXT first then CURRENT The vocabulary search order is Order Vocabulary 1 ASSEMBLER Now CONTEXT 2 FORTH Chained to ASSEMBLER 3 User s Vocabulary CURRENT if one exits 4 FORTH Chained to user s vocabulary 5 Literal Number The above sequence is the usual action of FORTH s text interpreter which remains in control during assembly HL 3FDC END CODE 3FAA CS 3F37 ENDIF 3ECD WHILE 3E4B BITSET 3DD1 JMP 3D91 LDX 3D51 ROR 3D11 DEC 3CD1 ORA 3C91 AND 3C57 TXA 3C1F SEI 3BE7 RTI 3BAF PHA 3B77 DEY 3B3F CLD 3A44 SEC 3A10 X 39DF 3984 PUTOA 394C PUT 3918 UP Figure 7 1 VLI
216. hich creates a user variable lt name gt The parameter field of lt name gt contains n as a fixed offset relative to the user pointer register UP for this user variable When lt name gt is later executed it places the sum of its offset and the user area base address on the stack as the storage address of that particular variable Offsets of 60 to 7F are available See Appendix G n name compute time DEFINING name run time variable A defining word executed in the form n VARIABLE name to create a dictionary entry for name and allot two bytes for storage in the parameter field When name is later executed it will place the storage address on the stack dddf VOCABULARY U voc link Leaves the address of user variable containing the address of a field in the definition of the most recently created vocabulary All vocabulary names are linked by these fields to allow control for FORGETting through multiple vocabularies VOCABULARY vocabulary A defining word used in the form VOCABULARY name to create in the CURRENT vocabulary a dictionary entry for name which specifies a new ordered list of word definitions Subsequent execution of name will make it the CONTEXT vocabulary When name becomes the CURRENT vocabulary see DEFINITIONS new definitions will be created in that list
217. hru N 7 Conventionally N 1 holds one byte and N N 2 N 4 N 6 are pairs which may hold 16 bit values See SETUP for help on moving values to the N Area It is very important to note that many FORTH procedures use N Thus N may only be used within a single CODE definition Never expect that a value will remain within N outside a single definition 7 5 5 SETUP Often we wish to move stack data values to the N area The word SETUP has been provided for this purpose Upon entering SETUP the accumulator specifies the quantity of 16 bit stack values to be moved to the N area That is A may be 1 2 3 or 4 only 3 LDA SETUP JSR Stack before N after Stack after TOP gt A high N gt A B low B SEC gt C C D D F F G low TOP gt G H high H 7 6 CONTROL FLOW FORTH discards the usual convention of assembler labels Instead two replacements are used First each FORTH definition name is permanently included in the dictionary This allows procedures to be located and executed by name at any time as well as be compiled within other definitions Secondly within a CODE definition execution flow is controlled by label less branching according to structured programming This method is identical to the form used in colon definitions Branch calculations are done at assembly time by temporary stack values placed by the control words
218. i e user Application programs use LITERAL which uses CLIT or LIT as appropriate WORD CMOV GI CODE COLD COMPILE CONSTANT STACK NOTATION DEFINITION GROUP ATTR addrl addr2 n MEMORY c move Moves n bytes from memory area beginning at address addrl to memory area starting at addr2 The contents of addrl is moved first proceeding toward high memory If n is zero or negative nothing is moved DEFINING code A defining word used in the form CODE name assembly code END CODI LH To set CONTEXT to the ASSEMBLER vocabulary and to create a dictionary entry for name When name is later executed the machine code in this parameter field will execute MONITOR cold The cold start procedure to adjust the dictionary pointer to the minimum standard and restart via ABORT May be called from the terminal to remove application programs and restart COMPILER compile When the word containing COMPILE executes the compilation address of the next non immediate word following COMPILE is copied compiled into the dictionary This allows specific compilation situations to be handled in addition to simply compiling an execution address which the interpreter already does n lt name gt co
219. ich caused the interrupt This code fragment serves as a typical example of all that is necessary to do at the code level for a wide variety of high level FORTH interrupt words The CODE word ARM turns OFF the interpretive interrupt inhibit bit bit 6 of INTFLG restores the FORTH interpretive pointer into the interrupted FORTH word and then jumps to FORTH s inner interpreter NEXT to continue execution ARM could be written in high level FORTH using C8 C and words but it must not be interfered with by a high level interrupt This interference cannot occur if the functions are done within a CODE definition The FORTH interpretive interrupt word for the 24 Hour Clock is T Another FORTH word L is used often by T These two words comprise th ntir interpretive interrupt service word T does just what the CODE definition interrupt routine did i e increment the hundredth s of a second byte by 5 and when it reaches 100 increment the seconds minutes etc The utility word L increments a certain byte by a given amount and checks it against the given limit If the limit is exceeded it zeros the byte and returns a true value so that the next byte can be incremented The arguments on the stack for L are limit 1 byte address increment T F The CODE definition word ARM stops execution of T The word switches FORT
220. identifies each FORTH error number and or message defines th rror meaning and describes the recovery action Appendix F Page Zero Memory Map defines the address variable name and general usage of page zero parameters Appendix G User Variables RAM Map defines the address variable name and purpose of each user variable The cold and warm start initialization values are also listed Appendix H ASC Character Set provides a list of 7 bit ASC codes in decimal and hexadecimal corresponding to 32 control functions and the 96 upper and lower case alphabetic numeric and special characters 1 2 Appendix I FORTH String Handling Words describes how to create string handling functions in FORTH Appendix J User 24 Hour Clock Program in FORTH illustrates a program written in FORTH colon and CODE definitions i e FORTH high level words and 6500 assembly language Appendix K Utility Functions explains how to determine the time it takes for a FORTH word to execute Appendix L RSC FORTH Versus FIG FORTH identifies words incorporated in each FORTH that are not included in the other FORTH Appendix M Selected Bibliography lists references to many popular and tutorial FORTH articles and books 1 2 REFERENCE DOCUMENTS Rockwell 29650N30 R6500 Programming Manual Order No 202 29650N31 R6500 Hardware Manual Order No 201 29
221. ies from most FORTH systems which return the parameter field pointer PFA This additional level of indirection is necessary to run separated heads and codes Type the word name after the word i e name FORTH will respond with OK for a found word and put the word s parameter field pointer address on the stack See Section 5 5 for description of the parameter field pointer address If not found the name is echoed with a and the stack is cleared Check TEST OP now and print the address in the dictionary HEX OK TEST OP RETURN OK 9 432 OK We can also run a VLIST to determine if TEST OP is in the dictionary and to verify the address returned by This is easy in this case since only two colon definitions have been added to the dictionary and these two entries are printed immediately Press any key to terminate VLIST VLIST 432 TEST OP 41B TEST OP 4DB TASK 3844 ADMP 3805 DUMP 37CF FORMAT 367E FMTRK 3674 BANKEXECUTE A key was pressed here OK While both versions of TEST OP are listed only the version at address 432 is valid since it was defined last 4 4 3 Print a Message with You can print a message of up to 127 characters with the word dot quote Start the message one or more spaces after the word Terminate the messag with a double quote Be sure to leave a space after the Now d
222. ifferent computers such as 6502 8080 and PDP 11 with very little change or none at all The RSC FORTH system follows the FORTH Interest Group FIG language model probably the most common dialect of FORTH and one closely aligned with the International Standard for the language The FIG model is available on the common small computers and is rapidly being implemented on others Therefore the R65F11 R65F12 microcomputer in conjunction with the R65FR1 Development ROM can be used to develop software for other computers and it can use published FIG model code regardless of the machine on which it was developed Published programs are commonly written entirely in FORTH with no machine code or other dependencies but designed so that short time critical words can be rewritten in assembly language for optimization on any particular host machine These programs can first be run unchanged then optimized only if needed As in any programming good style makes the application program easier to debug and verify and easier to read and modify when requirements change Many recommended FORTH practices are familiar from other language environments but some are different Practices such as top down design and bottom up coding and testing short modules indentation of control structures and a glossary as the principal documentation during development are discussed throughout this manual 3 2 DEBUGGIN
223. ilar manner Try 12809 135 RETURN 12674 OK Repeat these last two examples but insert CR before and after the word to display the result on a separate line 4 1 5 Multiply and Divide Multiply and divide also work in a similar manner Try the following 38 78 RETURN 2964 OK The word multiplies the top two items on the stack and leaves only the result on the stack The word divides the second item on the stack by the top item Try 13036 50 RETURN which displays 13036 50 260 OK Note also that the divide limited the result to an integer value the full answer is 260 with a remainder of 36 Other operations allow the remainder to be saved s Section 5 1 In all FORTH arithmetic and comparison words requiring two data items the operator behaves as if it were between the top two values on the stack Thus 13036 50 behaves as if it were 13036 50 Each number on the stack is 16 bits wide therefore these single numbers have the range 32768 to 32767 since the most significant bit bit 15 is used for the arithmetic sign This is enough for many applications but RSC FORTH also has double precision 32 bit numbers which are discussed in Section 5 1 4 1 6 Postfix Notation and Stack Operation Note that in the preceding examples the operators and were typed after their arguments not between them This style of arithmetic notatio
224. in XSAVE b Execute TSX to move the S register contents to the X register C Use RP to address the lowest byte of the return stack Offset the value to address higher bytes Ihe address mode is automatically set to X d Restore X from XSAVE As an example this CODE definition non destructively tests the second item on the Return Stack also the machine stack to see if it is zero CODE IS IT Is second item on Return Stack zero XSAVE STX Setup for Return Stack TSX RP 2 LDA Or second item s bytes together RP 3 ORA 0 2 IF If zero increment Y by one INY THEN TYA Save low byte XSAVE LDX Restore data stack PUSHOA JMP END CODE Push Boolean and zero onto data stack Low Memory Free Byte Top Item Low Byte lt RP 0001 X Top Item High Byte Second Item Low Byte Second Item High Byte Return Stack Z T 7 5 FORTH REGISTERS 7 5 1 Assembly Registers Several FORTH registers are available only at the assembly level and have been given names that return their memory addresses These ar LP Address of the Interpretive Pointer specifying the next FORTH address which will be interpreted by NEXT W Address of the pointer to the code field of the dictionary definition just interpreted by NEXT W 1 contains 6C the op code for the indirect jump instruction Therefore jumping to W 1 will indirectly jump via
225. ing colon definition example to measure the execution time of a FORTH word in this case DUP DECIMAL OK TDUP ON DUP OFF OK TDUP 68 OK Using this technique the execution time of most FORTH words defined using colon or CODE definitions can be measured Set up and run similar colon definition words as needed for your application Many problems can be programmed in FORTH using different combinations of FORTH words with differing resultant execution speed If speed is important measure the execution time of each approach to decide which solution to use If the execution time of a FORTH word defined in high level i e colon definitions is too long redefine portions or all of the word in assembly code i e colon definitions then remeasure Comparing the execution time of the word defined in assembly code versus FORTH will show the performance improvement For cases where th xecution time exceeds the 1 16 bit counter capacity other timing words can easily be defined to accumulate the time This page is intentionally left blank APP END RSC FORTH VI L ERSUS FIG FORTH This table is a comparison of RSC FORTH V1 6 and the FIG FORTH model from which it is derived a Words in RSC FORTH Word Name MBLER C ERLESS V1 6 that are not in F
226. inning address to suppress the output of trailing blanks The characters at addr n1 to addr n2 are blanks An error condition exists if nl is negative nossa INPUT OUTPUT dot Displays the number on the top of a stack The number is converted from a signed 16 bit two s complement value according to the numeric BASE The sign is displayed only if the value is negative A trailing blank is displayed after the number Also see D INPUT OUTPUT dot quote Used in the form ecee Accepts the following text from the input stream terminated by double quote If executing transmits this text to the selected output device If compiling compiles so that later execution will transmit the text to the selected output device At least 127 characters are allowed in the text If the input stream is exhausted before the terminating double quote an error condition exists WORD MOD 0 lt STACK NOTATION DEFINITION GROUP ATTR nl n2 FORMAT dot line Displays a line of text from mass storage by its line number n1 and screen number n2 Trailing blanks are suppressed nl m2 gt FORMAT dot R Displays number nl right justified n2 places No trailing blank is printed STACK dot S Displays the contents of the stack without altering the stack This word is very useful in determining the stack contents durin
227. instead preserved by the event in the Port B latches until the processor has time to read the port Caution should be xercised when using Port B since the bank switch instructions also use Port B If the bank instructions are not used however there is no conflict Table 9 3 Port A Control and Usage wane PORT B LATCH STROBE COUNTER B O is 8 y i i CNTB PAG VO SCCR7 0 SCCR 1 1 HARDWARE BUFFER FLOAT 2 POSITIVE EDGE DETECT 3 NEGATIVE EDGE DETECT 4 RCVR S R MODE 1 WHEN SCCR6 SCCAS SCCR4 1 5 APPLIES TO EITHER R65F11 OR R85F12 PORT SEE PIN DIAGRAM Fi i SERIAL 1 0 PAT vO SCCR6 0 a IHE s 1 9 2 SERIAL 1 0 The R65F11 R65F12 Microcomputers provide a full duplex serial I O channel with programmable bit rates and operating modes The serial I O functions are controlled by the Serial Channel Control Register SCCR The SCCR bit assignments are shown in Figure 9 2 The bit rate sometimes referred to as baud rate is determined by Counter Timer A for all modes except the Receiver Shift Register mode which requires an external clock The maximum data rate using the internal clock is 62 5K bits per second This assumes a 2 MHz internal clock The transmitter and receiver can be independently operated in different modes They can also be independently enabled or disabled The RSC FORTH Oper
228. into the dictionary but first save the starting address for later loading into the interrupt vector The code frag ment also called an orphan eliminates the slight overhead of the dictionary header In either case terminate the interrupt handler with an RTI to return to the interrupted program rather than NEXT JMP which returns control to the inner interpreter Before continuing you may want to review the R6500 interrupt processing features discussed in Chapter 9 of the R6500 Programming Manual The R65F11 R65F12 interrupt vectors normally available to the user are NMI 0040 NMIVEC IRQ 0042 IRQVEC PERFORM USER NMI PROCESSING Figure 8 1 Machine Level NM nterrupt Handling 8 2 0042 IROVEC VECTOR PERFORM USER IRQ PROCESSING Figure 8 2 Machine Level 83 RO nterrupt Handling AT PROGRAM INITIALIZATION AT FORTH WORD OR COMPILE TIME INTERPRETATION E ee E LOAD ADDRESS OF THE INTERRUPT PROCESSING WORD INTO INTVEC LOAD AODRESS OF THE INTERRUPT SERVICE ROUTINE CONTINUE SET INTERRUPT REQUEST INHIBIT BIT 6 1 IN INTFLG PERFORM INTERRUPT PROCESSING AT INTERRUPT OCCURRANCE SET INTERRUPT REQUEST IN INTFLG BIT 7 1 RESTORE IP RESET INTERRUPT REQUEST BIT 7 0 AND RESET INTERRUPT REQUEST INHIBIT BIT 6 0 IN INTFLG
229. is saved on the stack by the word HERE until the coding is complete then it is stored in the appropriate interrupt vector Notice that in both the above cases the interrupt vector was loaded after the interrupt handler was assembled This method allows an IRQ or NMI interrupt occurring immediately after the interrupt vector is loaded and the IRQ interrupt is enabled to be processed correctly 8 3 INTERPRETIVE INTERRUPT HANDLING PROCEDURE 8 3 1 Interrupt Service Routine To write a minimum length interrupt service routine using the procedure described in Section 8 2 to load the R65F11 R65F12 interrupt vectors this routine needs only to set bit 7 in the FORTH interrupt flag INTFLAG at 004A to one and return to the interrupted routine The format of the INTFLAG variable word is Bit No 0 7 INTFLG SOO4A x X X X X X Don t Care bit 6 Interpretive Interrupt Inhibit 1 Inh bited O Not Inhibited bit 7 Interpretive Interrupt Request 1 Requested O Not Requested 8 3 2 Interrupt Processing Word The desired IRQ interrupt processing procedure uses a high level FORTH colon definition word Load the code field address CFA of this interrupt handler word into the FORTH interrupt vector INTVEC a two byte user variable located at 005B and 005C Note that upon FORTH initial entry or upon executing FORTH word COLD this vec
230. ister IER determines the ability of a particular hardware event to cause an IRQ interrupt See Figure 9 2 for the detail bit assignments of these registers Note that unlike most other R6500 not have data direction reset state when RES is are config peripheral devices these single chip microcomputers do registers to control the I O ports The port is put in a driven from low to high The registers and I O ports ured as shown 9 1 PARALLEL I O The R65F11 has 16 A and Port B may be us programmed as an input or an output A number of the combination serial norma in Figure 9 3 before an external ROM is autostarted d either for input or output I O lines grouped into two 8 bit ports These two ports Port Each port line may be either independently or in groups of any I O pins are multifunction For example the channel lines use the Port A lines PA6 and PA7 These are protected from port I O instructions when they are programmed to perform special functions R65F 11 T Van PAO PA7 PAO PA1 POSITIVE PA2 PA3 NEGATIVE EDGE DETECTS PBO P87 LATCHED INPUTS rs 84 DSIPAO INPUT DATA STROBE AD A3 A12 RW A13 EMS PCO PC7 A4 A11 ADOR DO D7 DATA BUS PDO PD7 16 BIT R65F12 MULTIPLEXED FUNCTION PINS Figure 9 1 R65F11 and R65F12 Interface Diagram 9 2 Table 9 1 1 0 an
231. ister Serial Communications Control Register Serial Communications Status Register Serial Communications Data Register High Level Interrupt Flag Register High Level Interrupt Vector Low Level Interrupt Request IRQ Vector Low Level Non Maskable Interrupt NMI Vector 6 1 For example enter PB A 1 will be displayed Port B is at address 0001 To see the value in Port B enter HEX PB CQ An FF will be displayed if Port B has not been modified since reset A check of the words in the kernel shows that PB is not one of them The application programmer can however access PB The following definition does not cause system failure when the Development ROM is removed PB PB CQ The interpreter detects that PB is being used inside a colon definition and rather than compile the CFA of PB into the definition instead compiles a primitive that indicates the byte following it is a constant to be put on the Stack and then puts the value of PB in the next byte This is exactly what happens if you look up the actual address of Port B and use that number in the definition The following definition produces identical code to the previous example PB 1 CQ Each of the system variables function In this fashion 6 2 DEFINING WORDS 6 2 1 Creating Address Constants with C CON The defining word used to create the system address constant is a
232. ists the arguments it takes from the stack and the results returned and gives a short verbal description usually one to three sentences of its action Such a glossary completely describes the word as it is seen by any other part of the program When a new word is being tested all earlier words should have these descriptions available Therefore the programmer seldom needs to look at the source code of any other word the glossary fully describes its functions During testing and debugging only one word at a time needs to b xamined this greatly cuts down the need for program listings during development One important debugging procedure applies only to FORTH After a word appears to work correctly it must be tested to make sure that it does not take any u c nexpected numbers off the stack or return unexpected results One way to heck is to leave markers easily recognized numbers such as 1 2 and 3 on the stack and then execute the word being debugged After an operation use S to make sure that the markers are still on the stack below any arguments returned by the test word This check is important because otherwise the word may look like it works but causes later program crashes at unexpected and seemingly random places making the problem hard to debug SECTION 4 ELEMENTARY OPERATIONS This section provides a step by step description of elementar
233. its corresponding DO Immediate words are discussed in Section 5 4 22 An example of DO LOOP is a one millisecond time delay word this example assumes a 1 MHz internal clock rate MS N MILLISECOND DELAY 0 DO 5 0 DO LOOP LOOP CR TIME UP CR This word will cause delays of n milliseconds when used by putting n on the Stack and then typing the word To execute a 9 millisecond delay simply enter 9 MS At the end of the delay the message TIME UP is displayed Try it with larger delays e g 1000 to visually notice the delay time 4 6 2 LOOP The DO LOOP index always increments by 1 Another word LOOP allows other increments Each time around the loop it takes a number off the stack for the increment DO 2 LOOP would increment by 2 The increment can be computed and it can hens during loop execution It can also be negative Th following word causes an odd number in the range 1 to N to be printed ODD SERIES N PRINT ODD SERIES 1 CR DO I 2 LOOP Execute ODD SERIES with 25 as the input number don t forget to put the input number on the stack or a STACK EMPTY error may occur 25 ODD SERIES 1357911 13 15 17 19 21 23 OK 4 6 3 LEAVE LEAVE is another word used with DO loops If LEAVE is executed wi
234. ks like ERASE except that memory is initialized to ASC blank 20 instead of zeros Try HEX 200 100 BLANKS OK 200 C 2FF C CR 20 20 OK FILL allows memory to be initialized to a desired value In addition to the starting address third on the stack and the number of bytes to fill second on the stack the fill bit pattern top of the stack is specified Try HEX 200 100 FF FILL OK 200 ca 2FF C8 CR FF FF OK Try 200 2FE CR 1 1 OK Notice that the 2 s complement value 1 was displayed when 16 bit numbers were accessed Note also that HEX is not required if FORTH is already in the HEX mode 4 3 4 Dumping Memory with DUMP A block of memory can be displayed using DUMP A starting address second on the stack and the number of bytes to be dumped top of the stack are specified Try HEX 200 14 F8 FILL OK Fill 14 hex locations with SF8 Enter 200 14 DUMP lt RETURN gt Starting at 200 to display 200 F8 F9 F8 F8 F8 F8 F8 F8 F8 F8 F8 F8 F8 F8 F8 F8 210 F8 F8 F8 F8 FF FF FF FF FF FF FF FF FF FF FF FF OK 4 3 5 Moving a Block of Memory with CMOVE It is often useful to move a block of data from one area of memory to another This can be done with the word CMOVE which takes three arguments on the stack a from address a to address and a byte count It moves the given number of bytes starting with the first address to the area o
235. l addr assembly time RETURN Dy run time pop A constant which leaves during assembly the machine address of the return point which at run time will pull a 16 bit value from the data stack and continue interpretation addr assembly time RETURN nl n2 run time pop two At assembly time constant which leaves machine address of the return point which at run time will pull two 16 bit values from the data stack and continue interpretation WORD PUSH PUSHOA PUT PUTOA EAT STACK NOTATION DEFINITION GROUP addr assembly time RETURN run time push At assembly time constant which leaves the machine address of the return point which at run time will add the accumulator as high byte and the top machine stack byte as low byte to the data stack addr assembly time RETURN n run time push 0 a At assembly time constant which leaves the machine address of the return point which at run time will add a zero as high byte and the accumulator as low byte to the data stack addr assembly time RETURN nl m2 run time put At assembly time constant which leaves the machine address of the return point which at run time will write the accumulator as high byte and the top machine stack byte as low byte over th xisting data stack 16 bit value n1
236. l IROVEC SI GI H H FORTH RO VECTOR NIT INITIAL ER VIA I 0 UACR C SE ERIODL TBL C ERIODH TBH C O IER C N FU U pH H H DECIMAL L INCR OVER A SWAP OVER C IF 0 ROT C ELSE SWAP D THEN T NT STORE D INC lt DUP Co UJ E ROP OR B INT RUN VALUE O iz s LIMIT CHECK T FORTH LEVEL INT 99 TICKS 3 0 TEE IF 59 TICKS 2 IT 59 TICKS 1f 1 10 L SE 1 L ERRUPT SE RVICE O SEC COUNT CONDS MINUTES IF 23 TICKS 1 L HOURS THEN Figure J 2 Using an Interpretiv 1 100 SI CLOCK USING FORTH INTERRUPTS Eri Q 24 Hour Clock Program Interrupt Handler J 5 TH THEN E N ARM SMUDGE SIMILAR TO T CFA PUT ADDRESS ON STACK ASSEMBLER INTVEC SAVE INT VECTOR TY tod PI Pl vu OU n M OR S 58 HE T PRINT TIME TICKS CG HRS 2 R TICKS 2 C DUP DD BEGIN WAITING FOR A SECOND CHANGE TICKS 2 CQ OVER NOT UNTIL DROP HOLD gt TYP Gl TICKS 1 C DD MIN SAVE amp DISP S ENTER 30 CHAR ME SSAGE 601 DUP 30 EXPECT 600 BEGIN 1 DUP C 0 UNTIL
237. l devices famil operation characteristics of the R65F11 I O channel and timers other Rockwe y Special consideration must be given The techniques described can l single chip microcomputers e g the devices peripheral such as Interface Adapter PIA Interface Adapter VIA Asynchronous Communications R6520 Peripheral R6522 Versatile R6551 R6545 CRT Contro ler CRTC members of the R6500 peripheral however to the specific and R65F12 parallel I O ports serial however be applied to R6501 R6511 as well as Interface Adapter ACIA The R65F11 and R65F12 Microcomputers are organized as shown in Figure 9 1 with its registers occupying 32 addresses as listed in Table 9 1 R65F11 R65F12 interfac operates in accordance with the settings of four internal control rol Register MCR determines the type bus structure e Serial Channel Control Register SCCR selected latching of Port B and the operating modes of Timers A determines serial transmitter and receiver enable and operation mode the number of aracters per data word parity enable and parity odd even settings e Serial Channel Status register SCSR registers a The Mode Cont and B b Th Sh Es Th al The Interrupt Transmission and Wake Up statuses of the serial channel controls End of Enable Reg
238. l of Computer Calisthenics amp Orthodontia November December 1980 pages 40 43 Dessey R and M K Starling Forth Generation Languages for Laboratory Applications American Laboratory February 1980 pages 21 36 Ewing M S The Caltech FORTH Manual California Institute of Technology Pasadena CA 1978 Ewing M S and W H Hammond The FORTH Programming System Proceedings of the Digital Equipment Computer Users Society DECUS San Diego CA November 1974 page 477 FORTH Interest Group fig FORTH Installation Manual Glossary Model May 1979 Box 1105 San Carlos CA 94070 FORTH Interest Group FORTH Dimensions a bimonthly newsletter c o FORTH Interest Group arris K FORTH Extensibility or How to Write a Compiler in 25 Words or Less BYTE icks S M 115 118 James J S Orthodon James J S What Is FORT Mannoni M FORTH An Ext 19 1960 pages 175 178 FORT FORT s Forte is Tight August 1980 pages 164 184 ter Programming for Micro Computers tia May 1978 also in ACM S H A Tutorial Ini Dr troduction Dobb s Jo urna O GPLAN Notices October 1978 BYT tensible Path to Fficient Programs Electronic Electronics March 15 1979 pages f Computer Calisthenics amp E August 1980 pages 100 126 Design July
239. l systems just as stated Mass storage however is certainly required when the program size increases There are two likely ways to accommodate mass storage One is to have the mass storage be a part of the RSC FORTH system e g add a floppy disk controller and associated circuitry The other is to stick with a minimal RSC FORTH system and use a host system to download source code to the target system This host could be another RSC FORTH system an AIM 65 Microcomputer AIM 65 40 Microcomputer or other microcomputer system with mass storage The only real requirement on such a host system is that text can be entered and edited then transferred over a serial channel compatible with the RSC FORTH serial channel and respond to XON XOFF protocol It would also be desirable if the host could act as a terminal so direct communications with the R65F11 of R65F12 could be used during testing Most of the considerations made for PROM based systems depend on the nature of the target system The deciding factor is largely the memory allocation First it must be determined if the final target system requires any external RAM Dedicated applications that do all I O functions by manipulating the port lines for example a traffic light controller can rely entirely on the stack to provide temporary storage Applications that require a small array area i e magnetic badge readers can directly refer to the lower stack area Locations
240. lation stops and control is returned to FORTH haracters sent to the RSC FORTH system are not echoed to the sending unit Most terminals and computer systems that have the XON XOFF protocol can be used with SOURCE 3 QUR BOOQOJHAR GI 4 6 DO LOOPS 4 6 1 DO is LOOP The DO and LOOP statements allow repeated execution of a block of code For example the following definition creates a word SERIES which prints a series of 25 numbers zero through 24 SERIES PRINT A SERIES CR 25 0 DO L a LOOFE Now execute SERIES 0 1 2 3 43 00 7 8 9 TO dd 712 13 14 15 16 17 18 19 20 21 22 23 24 OK DO must always be paired with either LOOP or LOOP described in Section 4 6 2 The code section which they enclose can be of any length This code is xecuted repeatedly and an index value I is available When DO sets up the loop at run time it always takes two arguments from the stack The top stack number 0 is the initial index value of the loop and the second argument 25 is the final value plus one If the initial value is zero as is often the case the second argument is the number of times around the loop Also ordering the loop limits this way makes the loop upper limit more accessible from outside a definition We can see how this is done in the definition of NSERIES below
241. le Each use of that variable makes use of a code sequence variablel which executes the function of the particular variable Group Key Words GROUP ADDRESS Addressing Mode OP CODE Operation Code CONTROL Control Structures STACK Stack Addressing REGISTER Assembly Register CONDITION Conditional Specifiers RETURN Return of Control WORD 0 lt STACK NOTATION DEFINITION GROUP ADDRESS immediate Specifies immediate addressing mode for the next op code generated ADDRESS indirect Specifies indirect absolute addressing mode for the next op code generated gt ADDRESS indirect indexed Y Specifies indirect indexed Y addressing mode for the next op code generated ADDRESS indexed x Specifies indexed X addressing mode for the next op code generated m ADDRESS indexed Y Specifies indexed Y addressing mode for the next op code generated gt ADDRESS accumulator Specifies accumulator addressing mode for the next op code generated cc assembly time CONDITION zero less Specifies that the immediately following conditional will branch based on the processor negative flag status bit being negative N 1 i e less than zero The flag cc is left at assembly time there is no run time effect on the stack cc
242. led 3198 OLD OK 3457 1199 841 MPG 37 9 MPG OK 3665 1169 1038 MPG 24 1 MPG OK 3839 1199 1063 MPG 20 1 MPG OK 4017 1339 1150 MPG 21 3 MPG OK 4200 1329 997 MPG 25 0 MPG OK OLD 4200 OK Finally if you want to put the decimal points in the input numbers remember that RSC FORTH interprets this as a 32 bit number So for every number with a decimal point in it you will have two 16 bit numbers on the stack Program Enhancement You can redefine word MPG which will take such numbers and rearrange them to be acceptable to the original MPG This time the input is in whole miles cents and a tenth and dollars The 32 bit numbers go on the stack with the most significant part on top Since none of the numbers are even close to using the most significant 16 bit part simply drop them off the stack at the appropriate place and use the old version of MPG 10 5 MPG ODO CENTS COMPUTE MPG DROP UNUSED WD SWAP OTHER ONE DROP IT TOO MPG USE IT OVER RETURN Now test it with miles cents and a tenth and dollars 3198 OLD OK 3457 119 9 8 41 MPG 37 9 MPG OK Check to be sure OLD was updated OLD 3457 OK 10 6 SECTION 11 PREPARING AN APPLICATION PROGRAM FOR PROM INSTALLATION It is often desirable to install an application program writ
243. lizing Memory with ERASE BLANKS ad SE 2 A oh we eis he once e wale Sieh re Whe Stas ge fe ao Sos 4 3 4 Dumping Memory with DUMP 4 3 5 Moving a Block of Memory with CMOVE E Defining Your Own Operations ci Id eg apd G 42042 Coton DEFINICION see Goad eee bx eT os 4 4 2 Find a Word in the Dictionary with 4 4 3 Print a Message with o o ooooooooo ooo A Comment LING ta Re RUE UR mh o Re ea 9 Data Storage arc DO COOP AE Nudus 4 642 O EG RITE EE RISE AS 4 56 35 BAM a vw RUE T ve UNE A eee VET ETE EE alee a 4 Comparison and Logic Operations e 9 e Ye Bey nei CRS op ENING eC P DU 4 7 2 U OS and OS said whew iat AOV add hw eee Os 4 71 3 Logical Op rations wracked wovon VS ON ae ed ee as 8 Condit tonal Control Structures ercer ead 4 8 1 IF ELSE maw LHEN pt far Sh ae wc vas fo VER 458 2 Nesting Control Structures vacca we ie age gus 4 58 3 Masking and Setting Bits ip ee hea 4 8 4 BEGIN TROOPS 43h ee AA aa ea ees 4 9 1 Find Next Dictionary location with HERE 4 9 2 Use PAD for Temporary Storage 4 9 3 lI ncrement Me mory with tl imss 9 ev s 4 9 4 Exclusive OR Memory Using TOGGLE 10 Go0nstants and VarrabLles tn okt ote eere ets 40 1 CONSTANT A A hd a Rd Palla MARVAB UE ra ER 4 10 3 Defining Words i es y ey RE RR UE e
244. lue of the stack into the dictionary entry This is repeated until all of the vector elements are stored in the dictionary definition The remainder of the operation is the same as the definition The remainder of the operation is the same as the prior example for ARRAY BUILDS and DOES can be used to create much more elaborate data types such as Special array definitions which do bounds or other error checks at run time These definitions could be used during debugging and replaced with the regular b faster definitions for production use once you are assured that no out of ounds error will occur This page is intentionally left blank ON 6 SPEC AL OPERAT ONS RSC FORTH has many extensions not found in other standard FORTH packages System constants new defining words disk interface and general utilities 6 1 SYSTEM CONSTANTS Basically these extensions can be grouped into five categories of new words target compilation dictionary control There are a number of significant addresses in RSC FORTH corresponding to microcomputer functions such as input output ports channel controls These locations are of importance to the designer of RSC FORTH mode controls and serial systems for dedicated applications since these designs usually require the construction of I O structures not covered by the use of KEY EMIT A
245. m address constant for addr of Port A addr DICTIONARY Leaves the address of a scratch area used to hold character strings for intermediate processing The maximum capacity is 64 characters addr MISC P port b System address constant for addr of Port B addi MISC P port c System address constant for addr of Port C addr MISC P port d System address constant for addr of Port D addr MISC P port e System address constant for addr of Port tz addr MISC P port tf System address constant for addr of Port F nfa pfaptr DICTIONARY p f a pointer Converts the name field address nfa of a pointer dictionary definition to its parameter field address pfaptr WO RD PG PRI QUI QUI R ICK ERY W STACK NOTATION DEFINITION GROUP ATTR addr MISC P port g System address constant for addr of Port Port G n nth STACK pick Returns the contents of the nth stack value not counting n itself An error conditions results for n less than one 2 PICK is equivalent to OVER addr MASS U prev Leaves the address of a user variable containing the address of the disk buffer most recently referenced The UPDATE command marks this buffer to be later written to mass storage INPUT OUTPUT query Accepts input of up to 80 char
246. me RETURN nl n2 n run time binary At assembly time constant which leaves the machine address of a return point which at run time will pull two 16 bit values from the stack and push the accumulator high byte and the top machine stack byte as low byte to the data stack n addr cc assembly time CONDITION n addr cc assembly time CONDITION WORD CS ELSE END COD GI ENDIF STACK NOTATION DEFINITION GROUP cc assembly time CONDITION carry set Specifies that the immediately following conditional will branch based on the processor carry status flag being set C 1 The flag cc is left at assembly time there is no run time effect on the stack addrl 2 addr2 2 CONTROL else Occurs within a CODE definition in the form cc IF true part ELSE false part THEN At assembly time ELSE assembles a forward jump to just after THEN and resolves a pending forward conditional branch from IF The value 2 is used for error checking of conditional pairing At run time if the condition code specified by cc is false execution will skip to the machine code following ELSE E MISC end code An error check word marking the end of a CODE definition Successful execution to and including END CO
247. memory address b 8 bit with high eight bits zero C 7 bit ASC character with high nine bits zero GO pou 32 bit signed double integer most significant portion with sign on top of stack flag Boolean flag 0 false non zero true ff Boolean false flag value 0 B Nps aes 16 bit signed integer number UL 16 bit unsigned integer number ud udi 32 bit unsigned number EE Boolean true flag value non zero Pronunciation The natural language pronunciation of FORTH names is given in double quotes Integer Format Unless otherwise noted all references to numbers are for 16 bit signed integers The high byte of a number is on top of the stack with the sign in the left most bit For 32 bit signed double numbers the most significant part with the sign is on top All arithmetic is implicitly 16 bit signed integer math with error and underflow indication unspecified Capitalization Word names as used within the glossary are conventionally written in upper case characters Lower case is used when reference is made to the run time machine codes not directly accessible e g VARIABLE is the user word to create a variable Each use of that variable makes use of a code sequence variable which executes the function of the particular variable B 1 Attributes ATTR Capital letters show definition characteristics E May only be used within a colon definition
248. mpile CONTROL end if An alias for THEN See THEN addr n MEMORY erase Clears a region of memory to zero from addr over n addresses WORD ERROR EXECUTE EXPECT STACK NOTATION DEFINITION GROUP ATTR line in blk SECURITY error Executes error notification and restart of system WARNING is first examined If WARNING 1 the text of line n relative to screen 4 of drive 0 is printed This line number may be positive or negative and beyond just screen 4 If WARNING 0 n is just printed as a message number non disk installation If WARNING 1 the definition ABORT is executed which executes the system ABORT The user may cautiously modify this execution by altering ABORT RSC FORTH saves the contents of IN and BLK to assist in determining the location of the error Final action is execution of QUIT addr COMPILER execute Executes the definition whose code field address is on the stack The code field address is also called the compilation address addr count INPUT OUTPUT expect Transfers characters from the terminal beginning at addr upwards until a return or the count of n characters has been received Takes no action for n zero or less One or more nulls are added at the end of the text
249. mpile time DEFINING name n run time constant A defining word used in the form n CONSTANT lt name gt to create a dictionary entry for lt name gt leaving n in its parameter field When lt name gt is later executed it will push the value of n to the stack B 21 WORD CONTEXT COUNT CR CSP CURRI ENT STACK NOTAT ON DEFINIT ON addr context Leaves the address of a user variabl GROUP ATTR VOCABULARY e pointing to the vocabulary in which dictionary s be made during interpretation of th addr addr 1 n count Leaves the address addr 1 and the ch of text beginning at addr The firs must contain the character count n FOR earches are to e input stream MAT aracter count n t byte at addr The actual text starts with the second byte The ran Typically COUNT is followed by TYPE ge of n is 0 255 carriage return Transmits a carriage return to the active output device CR and line feed INPUT OUTPUT LF DIC TIONARY create A defining word used in the form CREATE lt name gt Creates a dictionary entry for lt name gt without allocating any parameter field memory When lt name gt is subsequently executed the addres s of the first left on the stack byte of lt name gt s parameter field is The code field contains
250. mum MAX 5 2 5 2 Unsigned Mixed and Double Precision Arithmetic 52 5 2 1 Entering Double Precision Numbers 5 3 5 2 2 Printing Double Precision Numbers 5 3 5 253 Other 32 Brt FORTH OpGratofs ul Ael 5 4 5 2304 Unsigned Compare Ux aria Roy SUE EO 5 5 5 2 5 Unsigned Multiply U and Divide U 5 5 5 2 6 Mixed Mode Operations M M and M MOD 5 6 5u2 17 MSC LINDA hed keel ee welt WEAR I eR EM een 5 6 5 3 QUEPput Formatting 22 id rU CR 5 17 5 3 1 S D t 4S SIGN and gt 5 7 Diez and HOLD vara dba EX XAVIER ACIER C 5 8 Dud SEIS exulueeuen tet ey se e rre kW recien epiac us vierte 5 9 5 4 1 Address String Data with COUNT 5 9 5 4 2 Output String Data with TYPE wv ee sewed eens 5 9 5 4 3 Input String Data with EXPECT 5 10 5 4 4 Suppress Trailing Blanks with TRAILING 5 10 5 4 5 Interpret a Number with NUMBER 5 10 5 4 6 Input a Number with NUMBER 5 11 V TABLE OF CONTENTS Section Title 2 5 Dictionary SETUCLUES dei A Oe ee eww Disowl FORTH Word SECLUCTEUCES int ee wad a a ee 5 5 2 Handling FORTH Word Addresses iii 9 4 5 5 3 FORTH Word Handling Examples 5 6 Vocabular ieS mee a d Ret EE aa Oso MOS DABLE A MS edere
251. n another bank with no problem of address translation The programming word shown here could transfer all ROM to a 2764 in bank BANK PROM 2000 400 DO cQ C350 1 BANK EC the program in RAM from 400 right up to the Development LOOP Note that C350 was used for the cycles to program because the 2764 requires 50 milliseconds per byte Once programmed the word can still in the PROM in bank 1 with RUN CFA 1 BANKEX ECUTE ven be tested by calling the main word while Assume the word to be tested is RUN then test it Caution should be observed concerning system variables unless RAM has been provided and initialized at 300 in bank 1 Bank 256 SFF is the main bank since this is the value of Port B at reset In order for bank switching to work Port B must be used in the chip select decoding of all memory chips or the window in which the bank switching can occur must be limited to those in which it is 6 5 6 Specifying Top of Memory Finally MEMTOP is provided to initialize the values of FIRST and LIMIT if it is not a full RAM system Note that LIMIT is 2000 and FIRST is 17F4 at power on These can be changed by entering n MEMTOP where n is the last location of RAM available plus one This page is intentionally left blank S ECT ON RSC FORTH ASS I iM
252. n is called POSTFIX or Reverse Polish Notation RPN It can represent complex formulas without any use of parentheses For instance 42 50 128 1090 3 would appear in postfix as 42 50 128 1090 3 Note that the operands the numbers are in the same order in the postfix and infix ordinary arithmetic expressions Don t forget to type and RETURN to display print the result If you are new to postfix you may want to follow this example by using stack diagrams as shown in Figure 4 2 This illustration shows the successive states of the stack after each number or operation has been processed Each column shows the stack at one time The number on top is the most accessible number on the stack ready to be used first by any operation which takes a number from the stack We say that this number is at the TOP of the stack In the execution of the postfix formula shown above 42 is placed on the stack first column of Figure 4 2 then 50 is entered The subtraction destroys those arguments and leaves the difference 8 You can follow the rest of the process similarly Each column in Figure 4 2 shows the stack at the time after each successive number or operation of the formula has been processed Note that any numbers which may have been below these numbers on the stack will be undisturbed Repeat the above example but insert S after each number and operator to examine the Stack contents after each oper
253. n easily be constructed in FORTH is described in Appendix Because there is no ready made standard you can decide how to represent strings internally Two formats are already in use within the system In one a length byte is followed by the string itself string length cannot exceed 255 characters The address of the string is the address of the length byte this is used to store names of words in the dictionary In the other format only the string itself is stored in memory its address is the address of its first character The length is stored separately and kept above the string address on the stack 5 4 1 Address String Data with COUNT The COUNT word returns the address second on stack of a character string and the number of characters e g bytes in the string top of the stack The character string can be up to 255 bytes in length COUNT operates on the address preceding the first byte of the character data which must contain the number of bytes of the character data 5 4 2 Output String Data with TYPE The word TYPE takes the address of the first data byte second on stack and the data byte count top of stack and outputs it to the active output device TYPE is usually preceded by COUNT which sets up the data address and byte count in a compatible format 5 4 3 Input String Data with EXPECT The word EXPECT see Section 4 11 2 can be used to read a stri
254. n the stack switches to the decimal mode and outputs the data in decimal when is commanded Now fetch and display the value in hexadecimal by EX 200 CR E80 OK CO T 4 3 2 8 Bit Store C and Byte Fetch CQ Similar words allow byte length data to be stored and fetched The word Ci c store stores the least significant 8 bits of the second item on the stack into the address determined by the number on top of the stack The word ca c fetch accesses the 8 bits stored at the address on top of the stack and stores it on top of the stack replacing the address Try HEX OK 41 200 C OK F4 201 C OK which stores 41 and F4 into addresses 200 and 201 respectively Display the contents of those address with 200 c8 201 C8 CR F4 41 OK 4 3 3 Initializing Memory with ERASE BLANKS and FILL Three words allow a block of memory to be initialized to various values ERASE fills memory with zeros 00 starting at a specified address second on the stack and continuing through the number of bytes specified top number on stack HEX 200 100 ERASE OK Spot check with 200 2FE CR 0 0 OK Note that if the contents of 2FF were fetched a non zero number may be displayed since fetches two bytes 2FF and 300 and address 300 was not erased The last byte could have been checked with 2FF C8 CR 0 OK BLANKS wor
255. n the accumulator Jump to PUSH BINARY or PUT PUSH will place the two bytes at the new bottom of the data stack PUT will over write the present bottom of the stack with the two bytes BINARY first pops two stack values four bytes then does a push Failure to push exactly one byte on the machine stack will disrupt execution upon usage The simplest version would use PUSHOA CODE ONE LDA USHOA JMP ND CODE Huey If the high byte of a result to be placed on the stack is zero and the low byte is in the accumulator the words PUSHOA and PUTOA are convenient They work the same as PUSH and PUT but add to or replace the data on the stack with a zero in the high byte position and the contents of the accumulator in the low byte position 7 8 ASSEMBLER SECURITY 7 8 1 Assembler Tests Numerous tests are made by the assembler to detect errors in structure and syntax These tests verify that All parameters used in CODE definitions are removed Conditionals are properly nested and paired Op codes are valid Address modes and operands are allowable for the op codes aap Note that a possible error not detectable by the assembler is referencing a word in the wrong vocabulary e g referring to 0 in the FORTH vocabulary rather than the Assembler vocabulary 7 8 2 Bypassing Security Occasionally we may want to generate unstructured code W
256. n used interchangeably Since these block sizes are commonly the size of a floppy disk sector of 128 or 256 bytes there are normally eight or four blocks per screen respectively however in RSC FORTH the floppy interface reads multiple sectors from the floppy at once Therefore the block size and the buffer size is the same as the screen size a Block Buffer A particular block is referenced by the FORTH word BLOCK which takes he block number as the argument If the block of data is in RAM LOCK returns immediately with the address of the buffer where th ata is to be found If the block is not in RAM BLOCK uses R W described below to fetch it from mass storage and put it in a uffer in RAM then returns the address of that buffer BLOCK also hecks to see if the data in a particular buffer needs to be written ut to mass storage before it uses the buffer for new data OQ TR OWE Each block buffer in RAM is four bytes larger than the mass storage block size Two of these extra bytes are at the end of the buffer and both contain ASC null characters 00 to mark the end of data The other two bytes located at the start of the buffer contain the block number and a one bit flag MSB that indicates whether or not the buffer contains data that must be written to mass storage before the buffer can be used for new data The layout of a block buffer is 12 1 LO
257. nced by LIST n MASS seek Causes drive selected to seek track n n MASS select Selects and activates disk drive number n WORD SMUDGI SOURCI SP SPG SPACI SPACI GI GI GI El n STACK NOTATION DEFINITION GROUP ATTR n di FORMAT sign Inserts the ASC minus sign into the pictured numeric output string if n is negative n is discarded but double number d is maintained Must be used between 4 and 4 a DICTIONARY smudge Used during word definition to toggle the smudge bit in a definitions name field This prevents an uncompleted definition from being found during dictionary searches until compiling is completed without error MONITOR source A procedure which allows batch compilation from the serial channel or an alternate input Compilation continues until FINIS is encountered FINIS alters serial input back to serial channel 222 STACK s p store Initializes the stack pointer from SO addr STACK s p fetch Returns the address of the top of the stack as it was before SP was executed e g 1 2 SP would type 2 2 1 INPUT OUTPUT Transmits an ASC blank to the active output device n INPUT OUTPUT spaces Transmit n ASC blanks to the active output device
258. ndicates single character literal Text scanning by WORD LOOP Location of Return Stack base Location of Parameter Stack base Initializes Return Stack Place 16 bit literal on the stack Puts Dictionary Pointer address on stack Puts Dictionary Pointer address of Heads on stack uts address of code field for Abort on stack uts address of number of characters line on stack Puts first address of data buffer on stack uts last 1 address of data buffer on stack Puts address of temporary storage PAD on stack FU FU FU A 11 A 18 PARAMETER Continued UR W addr Puts code field address on stack KHZ addr Unused user variable MODE addr Assembler variable APPENDIX B RSC FORTH GLOSSARY This glossary contains the definition of all words in the RSC FORTH vocabulary The definitions are presented in ASC sort order Stack Notation The first line of each entry shows a symbolic description of the action of the procedure on the parameter stack The symbols on the left indicate the order in which input parameters have been placed on the stack Three dashes indicate the execution point any parameters left on the stack after execution are listed on the right In this notation the top of the stack is to the right Symbol Definition addr addrl
259. ng into memory Unfortunately it does not return the actual length of the input string however you can find this length if it is needed by searching for the trailing nulls binary zero bytes 5 4 4 Suppress Trailing Blanks with TRAILING To eliminate trailing blanks of a message the word TRAILING is used If IRAILING is given an address of a string second on stack and a count top of stack such as that output by COUNT then TRAILING will adjust the count to commands if necessary to eliminate any trailing blanks in the string For example HEX 9 600 9 EXPECT RETURN allows nine characters to be entered into memory starting at 600 Enter ONLY5 followed by four spaces immediately after the RETURN following EXPECT note that OK will not be displayed until after nine characters are entered A five character message with four trailing blanks is now in RAM Check it with 600 9 DUMP 600 4F 4E 4C 59 35 20 20 20 20 0 XX XX XX XX XX XX OK Notice the terminating null character 0 placed after th ntered data Now enter 600 9 TRAILING S 5 character count less trailing blanks 600 starting address To see the full message less trailing blanks enter CR TYPE ONLY5 OK 5 4 5 Interpret a Number with NUMBER Most of the words needed for terminal input are described in
260. nitializing 600 to SFO HEX OK FO 600 C OK TOGGLE the value 600 55 TOGGLE OK Print the result 600 C RETURN A5 OK Note that both and TOGGLE could be performed otherwise using multiple FORTH words however these words are convenient and use less memory than multiple definitions 4 10 CONSTANTS AND VARIABLES 4 10 1 CONSTANT The word CONSTANT creates a new FORTH word which returns a value to the stack whenever it is executed For example 50 CONSTANT X creates a constant named X When this new word is executed it will return 50 to the stack Print the value of X with X RETURN 50 Constants are commonly used to give names to values which are fixed parameters in programs The same result could also have been accomplished by using a colon definition X 50 But the former is more efficient in both memory use and run time speed If it is necessary to change the value of a CONSTANT in RAM before storage of the program in ROM it can be done using the following technique new value name For example to change the 50 in the prior example to 78 use 78 XQ check it now with X RETURN 78 Note that trying to change the value of a constant by putting a new definition of the constant in the dictionary after compiling a word using it will not work Since existing linkage to the prior value will not change
261. ntering Double Precision Numbers RSC FORTH also supports 32 bit double precision 2 s complement numbers These are represented as two 16 bit numbers on the stack with the high order number on top Double precision allows positive or negative decimal integers in the range 2147483648 to 2147483647 to be used FORTH interprets an input number as double precision if there is a decimal point anywhere in it The location of the decimal point does not affect the value of the input number although the number of decimal places is saved in the system variable DPL in case you need to know it see Appendix G For example 555555555 and 555555555 are input as the same number only DPL is different Input the following numbers in double precision format and display the contents of DPL to check the number of decimal places in the input number 100 DPL RET 156 7 DPL 8 RETURN 1 365 12 DPL 8 RETURN 2 496 436752 DPL 8 RETURN 6 Double precision numbers are integers with the decimal point used only as a flag to indicate double precision the programmer must keep track of any implicit decimal point information Input the following small numbers in double precision format and print out the two 16 bit numbers that make up the number Notice that the most significant 16 bits is zero for positive numbers and is 1 SFFFF for negative numbers consistent with 2 s complement notation
262. on Example As a practical example here s a simple program that increments the value in Port A by one Enter the following words ODE POPA A INC EXT JMP ND CODE E zi Uso GI a The word CODE is first encountered and executed by FORTH CODI builds the name POPA into a dictionary header and calls ASSEMBLER as the CONTEXT vocabulary Note that the name after CODE must be on the same line b INC the INC executes INC is next found in the assembler vocabulary as th it assembles the byt instruction machine code read the value from Port A value new value to Port A When op cod E6 into the dictionary as This causes the R6502 CPU to increment the value and then return the Note that the FORTH assembler word names end with a significance of this is The 1 4 The comma distinguishes assembler words control The comma shows the conclusion of line of classical assembly be one compiles into the dictionary control words from FORTH Goog IF versus IF etc a logical grouping that would thus point at which code is generated source code a comma implies the The distinguishes op codes from possible hexadecimal numbers ADC ADD and BCC c FORTH executes your word definitions under control of the address int NEX address int
263. onal branch from IF At R T marks the start of an assembly sequence conditionally branched to from IF if cc is false At A T marks the conclusion of a conditional structure started by IF and resolves the forward conditional branch from IF if ELSE is not present At R T marks the conclusion of a conditional structure started by IF C 4 CONTROL ENDIF ETURN BINARY PUSH PUT POP PUSHOA PUTOA Continued A T addr 2 R T A T addr R T nl n2 n A T addr R T n A T addr R T nl n2 A T addr R T n A T addr R T Mm A T addr R T nl n2 Alias for THEN At A T leaves the address of a return point which at R T will pull two 16 bit values from the stack and push the accumulator H B and the top machine stack byte L B to the data stack At A T leaves the address of the R T return point which will add the accumulator H B and the top machine stack byte L B to the data stack At A T leaves the address of the R T return point which will write the accumulator H B and the top machine stack byte L B to replace the existing top data stack 16 bit value nl At A T leaves the address of the R T return point which will pull a 16 bit value from the data stack and continue interpretation At A T leaves the address of the R T retu
264. one argument from the stack it is tested for being less than zero or equal to zero respectively 0 lt leaves a true on the stack if the number is less than zero otherwise a false is left O returns a true if the number equals zero otherwise a false is returned 0 works the same as O written as two words similarly for 0 lt The one word forms are more efficient however faster execution O is equivalent to a logical not because it reverses the truth value of the top stack item it changes 0 to 1 and 1 or any other non zero value to 0 Experiment with the comparison operations HEX 10 20 lt RETURN 1 OK 20 10 RETURN O OK 5 0 RETURN 0 OK 5 5 0 RETURN 1 OK 10 10 lt RETURN O OK 10 10 U RETURN 1 OK 1020 2 RETURN 1 OK 8 0 0 RETURN 1 OK Note that the Boolean false value is always zero and any non zero value not only 1 is taken as a Boolean true However the value returned by these comparisons is always 0 or 4 7 3 Logical Operations Logical operations AND OR and XOR exclusive OR are provided These are bit wise operations Each takes two arguments from the stack and returns one result Each of the 16 bits of the result is obtained by applying the logical operation to the corresponding bits of the arguments All bit positions are treated independently
265. op number was duplicated 789 789 456 789 111 222 333 OK Let s remove and display the top four numbers from the stack before continuing CR RETURN which displays 789 789 456 789 OK Now enter O DUP CR S RETURN which displays 0 111 222 333 OK Notice that the top number was not duplicated DUP is usually used before an IF see Section 4 8 1 In the non zero case some action is usually performed using the value th xtra copy made by DUP is therefore removed by the IF processing In the zero case no additional action is performed thus the extra copy of the top number is not needed 4 2 3 Delete the Top Stack Item with DROP The word DROP deletes the top item on the stack Drop the zero now and check the stack contents DROP S RETURN 111 222 333 OK 4 2 4 Rotate Stack Items with ROT ROT rotates the top three items moving the third item to the top the previous top item to the second and the previous second item to the third For example 800 700 600 S RETURN 600 700 800 TET 222 333 OK Now rotate and display with ROT S RETURN which outputs 800 600 700 PTA 222 333 OK Now remove and display the top three numbers CR RETURN 800 600 700 OK 4 2 5 Copy a Stack Item with PICK PICK looks down any depth into the stack and copies the nth number from the top not counting the
266. ord is immediately compiled and entered into the FORTH vocabulary upon completion of ntry Upon commanding the new FORTH word the defined function is executed ORTH words can also be compiled and executed in a batch mode In this mode he FORTH words are compiled or executed upon entry from mass storage The ource program for colon definitions is not lost upon compilation with this echnique therefore changes can easily be made without requiring re entry of he whole program ct ct Qo ct Ao There are two methods of batch compiling in RSC FORTH The first method uses the standard FORTH technique of multiple RAM buffers and 1024 byte screens This technique is commonly used for manipulating saving and retrieving data files on mass storage This method is discussed in Section 12 he second method of batch compiling accepts an input from an intelligent erminal or download from another computer Entering the word SOURCE causes the SC FORTH system to enter an XON OFF protocol It begins by transmitting an XON haracter when SOURCE is first executed and accepts inputs until a null or arriage return is received or until the number of characters per line limit is eached It then transmits an XOFF character and interprets the received line hen interpretation is finished for that line an XON is transmitted to eestablish communications for another line When the word FINIS is executed or error is detected the compi
267. outine to mass The he calling is the last All the disk handler primitives are contained in t he kernel that is initialized to point to R W does not remove any parameters from the stack but expects to be passed he three on the stack is the memory address to be umber of the data on disk and the top is a ER etc are word outside the he kernel DI SK To read block 20 from the disk DRI vents to access the disk using the four EAD and DWR T m 6 4 2 Disk System Variables There are thr system variables that are very important to disk operations DISKNO CYLINDER and B SIDE DISKNO holds the number of the last disk selected This is used as an index when looking into CYLINDER These are actually four bytes reserved in CYLINDER one byte for each disk The track last used on each disk is recorded in its corresponding byte The variable B SIDE holds the number representing the number of 1K byte blocks per side of a disk The default value of B SIDE is 360 for a quad density disk The disk handlers will work with double or quad density disk drives By the number of the block passed to it using B SIDE DISK computes the number of the drive to be selected That number between zero through three is passed to SELECT SELECT turns on the motors if necessary an
268. owed by b will be compiled into the definition WORD CAT ca CASE GI CFA CLD WRM CLIT STACK NOTATION DEFINITION GROUP ATTR n INPUT OUTPUT characters line Leaves the number of characters default value 80 per input line addr byte MEMORY Ne fetch Leaves the 8 bit contents of the byte at the address on the top of the stack in the low order byte The high order byte is zero t name DEFIN NG case colon A defining word used in the form CASE name Creates a dictionary entry for name in CURRENT and sets the compile mode Words thus defined are called case statements The compilation addresses of subsequent words from the input stream are stored into the dictionary Intended for non immediate words only pta cata MISC c f a Converts the parameter field address pfa of a definition to its code field address cfa addr MONITOR U cold warm User variable containing the COLD WARM flag When equal to A55A reset does a warm start When not equal to A55A reset does cold start Checked by the kernel set by the user or development ROM PRIMITIVE Compiled within system object code to indicate that the next byte is a single character literal i e in range 0 255 Used only in system code not by application program
269. playing OK OK means that the system has correctly acted on your command and is waiting for another command to be entered Ihe OK is not shown in most of the examples however it is implied in all operations After RETURN is pressed the following is displayed 1 22 333 44 5 OK Notice that the cursor indicates the input character position A typing error during FORTH command or data entry can be corrected by pressing the DEL key lt BACK SPACE or RUB OUT on the terminal as necessary 4 1 1 Examine Stack Contents with S The word S pronounced dot s may be used at any time to examine the contents of the stack without altering the values or removing the numbers from the stack Try it by typing S RETURN The numbers entered in the prior section will be displayed in some examples the displayed data is underlined to distinguish it from entered data 5 44 333 22 1 OK The S word is very useful when learning RSC FORTH or debugging a FORTH program to determine the stack contents immediately prior to and or after executing a FORTH word 4 1 2 Print from the Stack using The print command removes a number from the stack and displays it and prints it if the printer is ON in the current I O number base In FORTH the print command is represented by a period and is called dot Type RETURN The 5 will be displayed and removed from the stack 5 O
270. previous word i e beginning of the previous name field This allows the dictionary to be scanned word by word beginning with the most recent word and moving back The last word in the dictionary has a link address of zero The parameter field pointer is a two byte pointer that points from the dictionary portion of the definition to the actual code of the definition This field is unique to RSC FORTH It is this pointer that allows RSC FORTH to operate with a separated kernel in ROM This provides the link from the dictionary to the kernel Note that there is no reciprocal link from the kernel back to the dictionary This is done to save space in the kernel This means it is possible to use the PFAPTR to find the parameter field but not vice versa The code address indicates the code to b xecuted depending on the type of word i e code SF874 for colon definition words SF8A0 for USER words F894 for VARIABLE words SF889 for CONSTANT words F9C5 for DOES words next address for CODE definition words The parameter field changes meaning depending on type of word If the word is a colon definition word the parameter field contains the addresses of the FORTH words their CFA s that make up the definition If the word is a CODE definition word then the parameter field contains the actual R6500 assembly code for the logic to be performed Examine the TASK word as an
271. r An 8 bit counter illustrates simple conditional looping O VARIABLE COUNTS 1 ALLOT CODE COUNT DOWN O 4 LDA COUNTS STA BEGIN COUNTS DEC 02 UNTIL NEXT JMP END CODE Execute the counter COUNT DOWN RETURN OK Dump the machine code for examination HEX COUNT DOWN NFA 20 DUMP 41F 8A 43 4F 55 4E 54 2D 44 4F 57 CE 11 4 30 4 30 42F 4 A9 0 8D IE 4 DO FE 4C 28 FA 4 44 55 4D 50 OK The breakdown of the machine code is CO L1F 120 12A L2C ZE 130 132 135 138 3A DO 4C 4 4 4 4 4 4 4 4 4 4 Fl 4 UNTS 28 F4 55 04 04 4E n 54 2D 44 4F 57 CE BNE DA S00 TA 0411 EC 0411 Lal Eel S D B J 043 MP F42 co O1 COUNTS Variable Name Field Start COUNT DOWN Name Link Field 04 PFAPTR 0430 Code Field 04 Parameter Field 11 30 Next In this example we use part of the RAM dictionary for the counter This counter is only 8 bits the 16 bit named dictionary location COUNTS however so after we creat we use ALLOT to back up over the extra byte and recover it for use 7 14 The definition of the word COUNT DOWN is a simple loop decrementing COUNTS until it hits zero then jump to NEXT First of course we clear COUNTS to its initial value by the LDA and STA instructions The initializing to zero is no problem because right after we
272. r The external RAM is required for FORTH user variables PAD and the Terminal Input Buffer TIB The Micro Monitor outputs a greater than sign gt to the system terminal at the beginning of a new line then waits for an input line from the operator The Micro Monitor is actually a very simple FORTH interpreter Much like the full FORTH interpreter the Micro Monitor allows the operator to enter FORTH words to be executed and numbers to be placed on the stack Since it is stand alone and operates without the aid of a development ROM FORTH words must be referenced by their Parameter Field Addresses rather than their name The way words and numbers are distinguished by the Micro Monitor is by the first character in the input stream on the line If that character is an N it is processed as a number and placed on the data stack If the character is a W the entry is considered to be a FORTH word which is immediately executed The characters following the first character must be hex digits The line entry is terminated with a carriage return Only one entry i e number or FORTH word can be made per line Entry into the Micro Monitor can also be gained by executing the FORTH word MON from the R65FR1 Development ROM As an example of the use of Micro Monitor the following sequence shows the entry of two numbers their addition and the outputting of the results The Micro Monitor was entered by either s
273. r 1 cc At A T assembles a conditional branch instruction to addrB BEGIN point based on condition code cc RII gt At R T conditionally branches to the BEGIN point if cc is false or continues ahead if cc is true A T addr 1 At A T assembles a JMP instruction to addrB BEGIN point RES gt At R T jumps to the BEGIN point C4 CONTROL REPEAT WHILE ELSE THEN Continued A T addr 1 addrW 3 R T A T addr 1 addr 1 addrW 3 R T A T adar 2 R T cc addr 2 A T addrl 2 addr2 2 RU oem A T addr 2 R T At A T assembles a JMP instruction to the BEG N point At R T jumps to the BEGIN point At A T assembles a conditional branch instruction to the instruction following REPEAT based on the condition code cc At R T conditional branches to the point following REPEAT if cc is false or continues ahead if cc is true At A T creates an unresolved forward conditional branch based on cc and leaves addr for resolution by ELSE or THEN At R T conditionally branches to the ELSE point or THEN point if ELSE is not present if cc is false or continues ahead if cc is true At A T assembles a forward JMP instruction to THEN and resolves the forward conditi
274. r own languages for particular applications greatly facilitating maintenance as requirements change FORTH keeps all definitions in a DICTIONARY The dictionary includes virtually all the object code of the system itself and of your applications Your own data structures may be in the dictionary or outside it at your option The internal structure of the dictionary is uniform and much simpler than the internals of most other languages therefore application programmers typically learn much more of the inner workings of the FORTH system Compiled FORTH code is extremely COMPACT in memory even compared to machine language The overhead associated with most FORTH systems is nearly non existent in RSC FORTH Since the runtime portions of RSC FORTH are in internal ROM there is no kernel to add to the user s code RSC FORTH can target compile user code and remove all the overhead of the dictionary structures By referring to the internal runtime kernel and user defined function RSC FORTH s hierarchical structure allows application code to build on itself increasing the memory advantage for larger programs and with little loss in speed FORTH code is recursive suited to multi tasking applications and can be programmed in RAM PROM or ROM FORTH is STRUCTURED There is no GOTO statement in the language IF and ELSE control structures and DO UNTIL an
275. r variable for check stack pointer Error operation terminates A 16 SECURITY Continued ERROR line in blk MESSAGE n WARNING addr FENCE addr WIDTH addr A 17 PRIMITIVES e CODE o LOOP n ABORT DO 1imit 1 start FIND addrl addr2 pfa b ff addrl addr2 f LINE nl n2 addr count LOOP o NUMBER OBRANCH BRANCH r gt gt GETT ENCLOSE addr c addr nl n2 n3 RO addr SO addr RP Gress LIT A 18 PARAMETER DP addr DP addr UABORT addr UC L addr UFIRST addr ULIMIT addr UPAD addr Execute error notification and restart system Displays message number n Flag for to message routine Prevents FORGET below this point Controls the number of significant characters of lt name gt compiled by compiled by CODE compiled by LOOP compiled by ABORT compiled by DO Run time Run time Run time Run time Run time procedure procedure procedure procedure procedure Searches the dictionary Virtual storage line primitive Run time procedure compiled by Converts ASC to numeric Run time conditional branch Run time unconditional branch I
276. rces disabled The serial channel of the microcomputer is set up for 1200 2 2 FERE R65F11 R65F12 INTERNAL SOFTWARE F400 KERNEL ROM UNAVAILABLE 4000 R65FR1 DEVELOP 2 2006 MENT ROM USER RAM ROM etc 0 0400 TERMINAL INPUT BUFFER TIB 0380 PAD USER VARIABLES 0300 0200 UNASSIGNED OPTIONAL R65F11 R65F12 0100 FDC MODULE STACKS SYSTEM VARIABLES PORTS 0000 NOTES 1 Required in every system configuration 2 Optional Figure 2 1 RSC FORTH Memory Map 2 3 NOTE FOR SYSTEM EXPANSION LE MORE RAM AND OR PROM ADDITIONAL DECODING WILL BE REQUIRED Figure 2 2 Typical R65F11 Microcomputer Minimum Hookup with R65FR1 Development ROM 2 4 baud asynchronous transmission assuming a 1 MHz internal clock with seven data bits no parity and two stop bits System variables including pointers that make the serial channel the system method of input output are down loaded from ROM to zero page in RAM for read write operation A test is made to determine the reset status If a user variable CLD WRM in memory location 030E contains a value other than A55A a cold reset is assumed In this case the low level IRQ vector IRQVEC the low level NMI vector NMIVEC and the high level interrupt vector INTVEC are forced to point to the system reset routine This prevents an unintentionally generated interrupt from crashing the system System variables TIB RO SO UC L UPAD UR W and BASE ar
277. rn point which will push a zero H B and the accumulator L B onto the data stack At A T leaves the address of the R T return point which will write a zero H B and the accumulator L B to replace the existing data stack 16 bit Value nl R POPTWO C 6 STACK RP TOP Nn tz a SETUP EGISTERS UP XSAV GI ETURN Continued A T R T A T A T A T A T A T A T A T A T A T A T addr nl n2 gt ada 101 hex Sada addr a0er addr addr addr At assembly time leaves th address of the run time return return which will pull two 16 bit values from the data stack and continue interpretation At assembly time leaves th address of the FORTH inner interpreter At A T used to address the bottom of the Return Stack At A T used to address the top item on the data stack At A T used to address the Second item on the data stack Leaves the address of a utility routine to move items from the Stack to the N area on z page Leaves the address of a nine byte work space in page zero Leaves the address of the pointer to the next FORTH execution address in a colon definition to be interpreted Leaves the address of the pointer to the base of the user area Leaves the address of the pointer to the code
278. roach provides the fastest response to an interrupt however since it is written in assembly language it may take longer to develop and check out An interpretive IRQ interrupt has a minimum length assembly language subroutine to service the interrupt and to initiate interrupt processing which is written in high level FORTH and is executed under control of the FORTH inner interpreter NEXT The general flowchart for th 8 3 Although the response to an interrupt may be longer with this approach is approach is shown in Figure the development and checkout may be done quicker and easier since the main interrupt processing is done in FORTH When developing interrupt dependent software regardless of the type of interrupt try to take small steps between checkout Carefully determine when system interrupts should be disabled or enabled Avoid using any interrupt Service routine that has not been first tested for logical integrity 8 2 MACHINE LEVEL INTERRUPT HANDLING Write a machine level interrupt definition see Section 7 1 handler in assembly language either as a CODE or as a code fragment described in Sections 8 2 1 and 8 2 2 If written as a CODE definition assign a name to the interrupt handler and later address it by that name to load the interrupt vector If incl written as a code fragment ude the assembly code directly
279. ror for the user s R W definition 9 16 gt Not assigned 17 COMPI The word just Don t use compila LATION interpreted must tion words inter ONLY be used in a pretively definition 18 EXECUTION The word just Don t use interpre ONLY interpreted must be tive words in a used outside of a definition definition 19 CONDI Omitted word or Pair conditionals TIONALS incorrect nesting correctly NOT PAIRED of conditionals 20 DEFINITION The current defini Finish definition NOT tion is not yet FINISHED finished 21 IN The word in question Cease trying to PROTECTED is below the FENCE FORGET a protected DICTIONARY word or move FENCE 22 USE ONLY Incorrect use of Use the word WHE the word gt only while LOADING loading E 4 DISK ERRORS Floppy disk operation errors are reported in the error byte left on the stack after DREAD or DWRITE is executed The individual meanings of each bit in this stack byte is defined in Table E 2 Bit No Table E 2 Disk Error Byte Description Description Disk is write protected Read Record Type error 1 Deleted Data Mark Write error Record not found Seek error in Format CRC error in 1D Field Lost Data error FDC device is busy El Hs Hex Address 000 00F 010 01F 020 03F 040 041 042 043 044 045 046 047 048 049 04A 04B 04C 04D 04E 04F 050 051 058 059 05A 05B 05C 0
280. rove program development productivity and program reliability FORTH is designed to satisfy both speed and programming efficiency requirements FORTH can be called a computer language an operating system an interactive compiler a data structure or an interpreter depending upon your point of view It was designed to combine the strengths of both compilers and interpreters The result is a unique language based on pre defined operations that minimizes software development time and costs supports structured programming and program modularity compiles interactively to ease debugging and to reduce programming errors compacts into small object code and executes extremely fast Additional words may be defined to allow usage by non programmers When all of the features of the FORTH language are combined with the utility of the RSC FORTH single chip microcomputer hardware the result is a powerful tool for the dedicated computer system designer Many extensions have been added to RSC FORTH that allow a very low cost few chip system to be both the development system and the final target system 1 1 RSC FORTH USER S MANUAL DESCRIPTION This manual is designed to provide both introductory instruction and detail language reference information If you are new to FORTH be sure to read and follow the manual chapter by chapter using a system which includes the R65F11 or R65F12 micro
281. rrors mentioned above in V1 5 RSC FORTH V1 6 is implemented in ROM devices for use with either the R6501Q or R6511Q ROM less microcomputer The R65FK3 is the Kernel ROM that operates in conjunction with the R6501Q or R6511Q and functions like the R65F11 or R65F12 FORTH microcomputer with internal ROM The R65FR3 Development ROM operates with the R6501Q R6511Q microcomputer and R65FK3 Kernel ROM in a similar manner as the R65FR1 Development ROM operates with the R65F11 R65F12 FORTH Microcomputer These parts are identified as R65FK3 Kernel ROM R327H 11 1 or 2 MHz and R65FR3 Development ROM R2953 11 1 or 2 MHz RSC FORTH V1 7 RSC FORTH V1 7 corrects all the errors mentioned above in V1 5 RSC FORTH V1 7 is implemented in the following parts R65F11 FORTH Microcomputer R1100 15 1 MHz or R1100 16 2 MHz or R65F12 FORTH Microcomputer R1200 13 1 MHz or R1200 14 2 MHz and R65FR1 Development ROM R2952 13 1 or 2 MHz Xii SECTION 1 INTRODUCTION FORTH is a unique programming system that is well suited to a variety of applications Because it was originally developed for real time control applications FORTH has features that make it ideal for machine and process control data acquisition energy and environmental management automatic testing and other similar applications The speed performance of assembly language is required in many of these applications however a high level language is often desired to imp
282. rt PORT LDA Fetch one byte 0 lt IF N DEC If D7 1 decrement N ELSE N INC If D7 0 increment N THEN Continue on 7 6 3 Conditional Nesting Conditionals may be nested according to the conventions of structured programming That is each conditional sequence begun IF BEGIN must be terminated THEN UNTIL before the next earlier conditional is terminated An ELSE must pair with the immediately preceding IF BEGIN code always executed Cs IF lt code if carry flag set gt ELSE lt code if carry flag clear gt THEN lt loop until zero flag is non zero gt O NOT UNTIL lt code that continues onward gt Next is an error that the assembler security will reveal CODE lt name gt BEGIN PORT LDA 0 IF TOP INC 0 UNTIL ENDIF The UNTIL will not complete the pending BEGIN since the immediately preceding IF is not completed An error trap will occur at UNTIL and error number 19 conditionals not paired will be generated To delete th rroneous code from the dictionary first SMUDGE the word to allow finding it then FORGET it and correct the source code and recompile 7 6 4 Some Nesting Examples a An 8 Bit Counte
283. s Jp rd TUS a kodara dr her oA eeu Rud s rt M Mete nd EUR od 4 0 5 AO eere ue tue A dt Said iv Bee 21 1 24 1 24 BPP BD BoB AB Hs BPR ds gt 23 1 23 1 23 24 1 25 26 21 28 29 29 30 32 33 33 34 34 39 TABLE OFCONTENTS Section Title Page 411 Changing the Number BASE ul gine ate A io 4 36 4 12 Output NOTAS al AA a I E d ROUEN CEU 4 37 4 12 Print Right Justified with sR 2 s eedu 4 37 4 12 1 Output Spaces with SPACE and SPACES 4 50 4 12 3 Output a Character with EMIT 4 37 4 12 4 0 tput sa String with TYPE sich satis beet od 4 38 4 12 5 Prepare to Output a String with COUNT 4 38 4 13 TInpub Words A SS es eck AAA Nee Oe ged IE ge te 4 39 4 13 1 Input a Character with KEY e m ng 4 39 4 13 2 Input a String with EXBECT ced oats ate 95 5 4 40 4 13 3 Test for Input with TERMINAL 4 41 5 Advanced Operations 5 1 Other Single Precision Arithmetic Operations 5 1 5 1 1 Modulus Operators MOD and MOD 5 1 5 1 2 Absolute ABS and Negate NEGATE 5 1 5 1 3 Simple Increment and Decrement 1 2 LS gd ARA RUE ele ux ew Aa RAUM OU SL 5 1 4 Minimum MIN and Maxi
284. s are conventionally used on both address and mask values for program clarity The mask of course need not be a literal value as shown in these illustrations it could be computed perhaps by previous logical operations or input from the terminal etc To turn ON the last three bits of the word on top of the stack leaving all other bits unchanged execut 0007 OR The OR operation as described earlier does a logical OR of each bit independently The sign bit is treated like any other In these examples we will assume that HEX has been executed to set the number base to 16 Similarly to turn OFF the last three bits use FFF8 AND To test if any of the last three are ON use 0007 AND The stack top will now be zero if none of the last three bits were ON and non zero otherwise This value can be used as a Boolean by IF UNTIL or WHILE but be careful if the value is used as input to another AND or OR input to these operations should be a Boolean zero vs one not zero vs non zero If such further logic is to be done use which leaves the truth value unchanged but converts the zero non zero result into a more correct zero one Boolean Use 0007 AND 0 2 0 or 0007 XOR to complement reverse values of the last three bits of the top stack word To complement all bits use FFFF XOR which could also be written 1 XOR because the numeric repr
285. s to be generated These do not necessarily need to be saved for the final system f Re enter the source code to recompile This can be done with LOAD from disk or SOURCE from a host computer 11 3 Add the autostart pattern 1 e enter AAAA AUTOSTART lt name gt where AAAA 1K page boundary to be used and name is the main starting point routine Transfer the image to PROM with ADMP or EEC as described in Section 6 11 4 SECTION 12 NTERFACING TO MASS STORAGE 12 1 OVERVIEW RSC FORTH includes all of the fundamental words needed to interface with and ffectively use mass storage devices This chapter provides directions and guidelines on how to interface to a floppy disk however the procedure may be easily modified to include other peripherals Before you begin you must have a mass storage device in correct functioning order and you must have enough memory added to the R65F11 or R65F12 microcomputer to hold two FORTH screens The minimum RAM requirement for buffers is 2056 bytes but a practical minimum for the system is 4K bytes although 6K is more reasonable and a full 8K is better 12 1 1 Mass Storage Terminology FORTH accesses mass storage in uniformly sized pieces called blocks and keeps data or source code in RAM in 1024 byte pieces Called screens If the block buffer is 1024 bytes then the terms block or screen are ofte
286. sed with caution The words are used like this 10 WIPE places blanks in screen 10 and 10 LIST verifies this To enter text use gt LINE like this 3 gt LINE THIS LINE OF TEXT GOES ON LINE 3 This text will be placed on line 3 and the rest of line 3 will be blanked in case there was old text on it Use gt LINE to place text into screens to make a simple editor Test these words by loading the screens and trying them out Then use the simple editor to make a enhanced editor that takes advantage of any features that your particular setup has After a screen has been created or edited the new information must be written to the disk before that screen is compiled This can be done with a FLUSH before the LOAD 12 8 APPENDIX A RSC FORTH FUNCTIONAL SUMMARY This appendix contains a summary of the RSC FORTH word definitions grouped by area of primary function each word Stack Notation Consult Appendix B for the detailed definition of The stack operation is denoted in the parentheses The symbols on the left indicate the order in which input parameters must be placed on the stack prior to FORTH word execution point Three dashes indicates the FORTH word execution Any parameters left on the stack after execution are listed on the right The top of the stack is to the right
287. side effects to save room MOVE I UP DOWN L P EFT R vok E LOOP EG NK EY 30 down left right using UP When used in a large definition the desired response MOVE makes it possible for yo to CASE GHT TO FROM the names of the functions imply their actions H and 2 MOV u to ent I AGAI N increase t N flexibility expanded MOV definition of MOVE LOOP B E LOOP EG NK EY 6 OVER U defin T causes a movement to t an operator could pus The definition could be as follows and FROM A selective an entry of 0 MOVE he ha r the keys 0 through 5 and command and from repeatedly ition is needed An entry other than 0 5 in the probability cause system failure or Error checking was omitted from interpreter in Operating speed and give the programmer maximum Error checking can easily be accomplished as in the following IF MOVE ELSE one per keystroke CASE performs no at a minimum CASE THEN AGAI on More elaborate forms of error checking are also possible The code that interprets CASE definitions is itself the product of a BUILDS DOES structure The DOES portion the interpreter is actually in th
288. single precision quotient top of stack and unsigned single precision remainder second on stack The following example gives a positive quotient and unsigned remainder 120031 4 U RETURN 30007 3 Note that another example 140035 4 U RETURN 30528 3 appears to give a negative quotient and unsigned remainder In the single precision format a number between 32 768 and 65 535 is displayed as negative unless printed as a double precision number The following example forces the quotient to a double precision number and prints it along with the remainder 140035 4 U O D RETURN 35008 3 5 2 6 Mixed Mode Operations M M and M MOD Some mixed mode operations are also available The operator M m times multiples two signed numbers and returns a signed double precision product Two examples illustrate the operation 4532 8765 M D RETURN 39722980 4876 5467 M D RETURN 26657092 The operator M m divide divides a double precision number second on Stack by the single precision number on top of the stack and returns a signed single precision remainder second on stack and signed single precision quotient top of stack Try this example 564755 500 M RETURN 1129 255 The word M MOD m divide mod divides a positive double precision number second on stack by a positive single precision number top of stack returning
289. ss storage buffer flag run time CONTROL T addr n compile time until Occurs within a colon definition in the form BEGIN UNTIL At run time if flag is true the loop is terminated If flag is false execution returns to the first BEGIN UNTIL structures may be nested At compile time UNTIL compiles OBRANCH and an offset from HERE to addr n is used for error tests addr PARAMETER U u pad Leaves address of the user variable containing the address of the temporary storage area PAD MASS update Marks the most recently referenced block pointed to by PREV as altered The block will subsequently be transferred automatically to mass storage should its buffer be required for storage of a different block addr PARAMETER u read write Leaves the address of the user variable containing the code field address of the mass storage I O word Initialized to ABORT on a cold start addr MASS U use Leaves the address of user variable containing the address of the block buffer to use next as the least recently written WORD USER VARIABLE VOC LINK VOCA BULARY STACK NOTATION DEFINITION GROUP ATTR pasas DEFINING user A defining word used in the form n USER lt name gt w
290. string functions and are not described NG STRI STRI The and For Crea When ot t TYPE NG creates a word in the dictionary up to 255 characters string is initialized to all spaces with a zero at the end the maximum length at the beginning example 30 STRING AS tes a string named AS which has room for 30 characters the name AS is executed the current length and the address he text is put on the stack in the order required for the word enters text into an intermediate buffer called IB if used in the immediate mode In the compile mode the text is put into the dictionary In either case the length and text address is left on the stack Text is terminated by another S S moves th ntire string text from one string to another for example COWS EAT CORN AS S puts the text COWS EAT CORN into the string AS Also as an example define another string BEST and move AS into it 40 STRING BEST AS BEST S MIDS MIDS gets the m characters of a string starting at the nth character position for example 6 3 AS MIDS TYPI E will print the word EAT LEFTS LEFTS gets the left most n characters of a string for example 3 BEST LEFTS EYR E will print the word COW RIGHTS In like manner RIGHTS gets the right most n characters of a string The sequence
291. sult of that comparison always false would be OR ed with the voltage that was on the stack before this phrase was extended 4 8 CONDITIONAL CONTROL STRUCTURES The following FORTH control structures test a Boolean result generated by the comparison or logical operations and direct the flow of program execution accordingly 4 8 1 IF ELSE THEN As with other control structures the IF and THEN must be used as a pair if they are not error message 19 or 20 will be generated s Append compile time Any correct block of FORTH programming may occur between the IF and the THEN The IF takes one argument a non zero the code between ix m B at Boolean value from the stack If it is true IF and THEN is executed if false zero that code is skipped In either case control resumes with the THEN For instance GET VOLTAGE 8 gt HOT OR IF SHUT DOWN THEN will execute the predefined operation SHUT DOWN if the previously defined word GET VOLTAGE returns a value greater than 8 or HOT returns true or both An optional ELSE clause allows a block of code to be executed only if a test is false For example the simple control loop 10000 0 Loop 10000 times DO GET VOLTAGE 8 gt HOT OR Danger LOOP IF GO SLOWER ELSE GO FASTER T
292. t 5 A word that will limit numbers to a range between 1 and 9 uses the following colon definition RANGE 1 MAX 9 MIN For example 6 RANGE lt RETURN gt 6 1 RANGE lt RETURN gt 1 O RANGE lt RETURN gt 1 0 is smaller than 1 9 RANGE lt RETURN gt 9 10 RANGE lt RETURN gt 9 10 is larger than 9 5 2 UNSIGNED MIXED AND DOUBLE PRECISION ARITHMETIC The FORTH stack is 16 bits wide and the numbers we have seen so far are signed values internally formatted in 2 s complement binary arithmetic In this number representation bit 15 the most significant bit contains the arithmetic sign and bits 0 to 14 contain the numeric magnitude value A 0 in the sign bit indicates a positive number while a 1 indicates a negative number A positive signed 16 bit number may range from 0 0000 to 32 767 S7FFF while a signed negative number may vary from 1 SFFFF to 32 768 8000 Signed values are used most often for arithmetic calculations 16 bits can also hold an unsigned number where bit 15 is interpreted as an additional order of magnitude rather than the arithmetic sign In this case bit 15 represents a value of 32 768 2 15 with the sign implicitly positive The value of a 16 bit unsigned number may therefore range from 0 0000 to 65 535 SFFFF Unsigned values are used most often for addresses 5 2 1 E
293. t from this form the word COUNT takes the address and returns the arguments required by TYPE Therefore COUNT TYPE displays a string given the address of its length byte Try the following HERE TYPE COUNT CR TYPI GI More advanced output operations are discussed in Section 5 3 Output Formatting These allow you to create your own output formats which may include such characters as decimal points dollar signs and commas More on string handling is discussed in Section 5 4 4 13 INPUT WORDS FORTH handles input by taking all characters tokens separated by spaces and first trying to look them up in the dictionary If the token is not in the dictionary the system tries to make a number of it using the number base currently in effect Then if the token contains a non digit character the system reports an error condition by typing the token followed by a question mark indicating an unrecognized word see Appendix E Most programs can use the FORTH system itself for terminal input You type the numbers onto the stack and execute operations to use them Many programs run without a terminal so no special input is needed You seldom need to write operations to accept input from the keyboard except for turnkey programs which do not run under the FORTH interpreter i e which do not give the OK to the user When special input is required several primitive operations are available
294. t which leaves at assembly time the address of the pointer to the code field execution address of the FORTH dictionary word being executed Indexing relative to W can yield any byte in the definitions parameter field For example the instructions 2 4 LDY W Y LDA will fetch the first byte of the parameter field WORD WHILE XSAV GI STACK NOTATION DEFINITION GROUP addrB 1 addrB 1 addrW 3 CONTROL assembly time run time while Occurs in a CODE definition in the form BEGIN cc WHILE REPEAT At assembly time WHILE assembles a conditional relative branch instruction to the instruction immediately following the REPEAT based on the condition code cc At run time WHILE controls the conditional branching to just past REPEAT If the processor status bit specified by cc is true WHILE continues execution through to REPEAT which then branches back to BEGIN If cc is false a jump is made to just after REPEAT and execution continues ADDRESS indexed indirect X Specifies indexed indirect X addressing mode for the next op code generated addr assembly time REGISTER x save Used in a CODE definition in the form XSAVE STX or XSAVE LD
295. target compiled code with separated dictionary headers The latter is called headerless code from having its dictionary header information heads code portion codes for short R65F12 single chip computer The RSC FORTH kernel or RSC FORTH ROM is al be added as overhead to the target compiled system as small as a few hundred bytes definitions referring to words outside the kernel th Development ROM will not be See Table 2 1 for a list of kernel words can be installed in target systems consisting only o stand alone The R65FR1 The unique field called the PFAPTR relieves RSC FORTH for short in line with its in ROM inside the R65F11 or ways available and need not Simple programs can be made As long as the operator is careful not to write 71415373 and the program in a ROM or EP disks or serial channel buffers etc Unlike other FORTH systems ROM Programs t Programs resultant program can needed in the final system hat do not need external RAM f the R65F11 or R65F12 a that require the use of the will need one additional RAM chip and decoding to hold the dictionary information is not lost in target compilation but rather is stored in separate memory It too may be saved if desired This can be an invaluable feature for debugging the compiled program Since the target compiled program can be run directly in whole or in parts wh
296. tee A er qu rte era E xe s APPENDIX 0 EGTCORS ecu A AO AA Mx RE Be APPENDIX P Selected Bibliography e Rau Iv Rot IS ix Page 2 5 12 5 12 6 12 7 A 1 2i CHL D 1 Figure NN NP Ru lol RD o 5 FWD t Cj XO XO XO XO XO XO XO XO LO OO OO OO 4S BN F2 000 1001 45 WN T N Title RSC FORTH Memory Map LIST OF FIGURES Typical RS65F11 Microcomputer Minimum Hookup with R65FR1 Development ROM Auto Start ROM Code Example VLIST of RSC FORTH Words Stack Diagram of Postfix Example VLIST of RSC FORTH Assembler Words Machine Leve Machine Leve Interpretiv nterrupt Handling RQ Interrupt Handling Interrupt Handling R65F11 and R65F12 Interface Diagram Register Bit Assignments ation of RES Initiali Serial Communication Interval Timer Timing Diagram Event Counter Mode I O Ports and Registers Bit Allocations Pulse wWuvdth Measurement aot da sada A di IR aes Counter B Retriggerabl Interval Timer Mode Counter B Pulse Generation 24 Hour Clock Program Using a Machine Level Interrupt Handler nd js we dene qr uar roe ade ire eral anus 24 Hour Clock Program Using an 1 Inte err pt Handler i i eee Shere wis ol
297. ten in FORTH into one or more PROM ROM devices for immediate operation upon microcomputer power turn on i e without requiring entry into the FORTH interpreter or recompilation of the application FORTH source code This section describes a method to develop an application program written in FORTH as normal or target compiled headerless code how to locate it for execution from either RAM or PROM ROM and how to cause one word to be autostart executed at power on or reset The RSC FORTH System was designed to easily autostart a dedicated program The RSC FORTH Operating System initializes all variables required by the kernel at reset then searches for an external user program to autostart Functions included in the development ROM that make preparation of programs for PROM ROM easy 11 1 PROGRAM DEVELOPMENT The first step in preparing an application for PROM is naturally to develop the program itself There are a number of viable options to choose from but some sort of development system must be created The RSC FORTH system is truly unique in that the target system which the program is being developed for can actually be the system used to do the development The only additional cost in designing a product that can be its own development system is the overhead required to support the development ROM a 28 pin socket and decode logic It is entirely possible to do complete developments for smal
298. ter B interrupt flag will be set if the counter underflows before a positive edge occurs on the CB line Figure 9 8 illustrates the operation b Asymmetrical Pulse Generation Mode Counter B has a special Asymmetrical Pulse Generation Mode whereby a pulse train with programmable pulse width and period can be generated without processor intervention once the latch values are initialized In this mode the 16 bit Latch B is initialized with a value which corresponds to the duration between pulses referred to as D in the following description The 16 bit Latch C is initialized with a value which corresponds to the desired pulse width referred to as P in the following description The initialization sequence for Latch B and C and the starting of a counting sequence are as follows see Figure 9 9 1 The lower 8 bits of P are loaded into LLB by writing to address 001C and the upper 8 bits of P are loaded into ULB and the full 16 bits are transferred to Latch C by writing to address location 001D At this point both Latch B and Latch C contain the value of P 2 The lower 8 bits of D are loaded into LLB by writing to address 001C and the upper 8 bits of D are loaded into ULB by writing to address location 001E Writing to address location 001E also causes the contents of the 16 bit Latch B to be downloaded into the Counter B and caused the CB output to go low as shown in Figure 9 9
299. terpreting the word three overlay words ar EL INPUT INPUT PROCESS in the load screen and OUTPUT defined befor the dummy word LEV and that these words are commonly used by the three overlays g load screen might look like this should This phrase discards the previous overlay and The process of overlays is Note that the This ensures that the overlay words will not be forgotten by the overlays themselves 12 6 The process of overlaying can be a manually directed one or if desired the next overlay can be called as the last action of the current overlay The process of over The methods out laying can then continue indef initely and unattended lined above for enhanced use o f mass storage are very useful in actual practice even though the methods are quite simple FORTH is capable of much more By using the defining words BUI LDS and DOES different classes of new FORTH words can be created to take advantage of other mass storage or external facilities 12 4 SOURCE COD E EDITING The many different mass storage devices terminals and user preferences make it impossible to provide more than a start at putting source code onto FORTH Screens Four useful namely LINE 7 LINE gt L defines a word useful for initializing screens used for text called WIPE in RSC FORTH
300. thin a loop it will set the limit to the index value causing the loop to exit when LOOP or LOOP is next executed LEAVE and also the index I can only be used inside a DO loop 4 7 COMPARISON AND LOGIC OPERATIONS The DO loop is one form f structured control in FORTH Other structures HI described later IF EN ELSE ars THEN BEGIN UNTIL BEGIN ice nd BEGIN AGAIN may test Boolean values truth vales ET control program execution Comparison and logic words place O tafa iT WHILE REPEAT a p E Booleans on the stack and then the control words use these values ARA E A ane lt Simple FORTH comparison words are lt less than gt greater than and equal Each of these operations takes two arguments from the stack destroying those arguments and returns one result a Boolean to the stack The second item on the stack is compared to the top item in accordance with the FORTH word If the comparison is true a true 1 is returned 1f false a false 0 value 4 7 2 U lt 0 lt and 0 Other comparison operations are U lt 0 lt and 0s U lt unsigned less than compares the top two stack numbers as unsigned 16 bit integers see Section rd E 0 zero less than and 0 zero equals differ from the others in taking only
301. times but the words in the BEGIN UNTIL loop will always execute at least once since the test is made at the end of the loop not the beginning Note the use of 0 equivalent to a logical NOT to reverse the truth value returned by HOT A BEGIN AGAIN structure creates an infinite loop AGAIN takes no arguments from the stack it always causes control to return to its corresponding BEGIN This structure could be used in a real time control program to execute a final procedure until interrupted It is also possible to exit this loop with a S word All of these structures can be nested within any others Again avoid long or complicated definitions Short definitions make programs easier to read debug and modify 4 9 DATA STORAGI GI How can you get an address of available memory to use for data storage One way to find available memory for data structures is to use the top of your RAM memory and work down since your word definitions start at 411 and work up For instance if you have 8K of RAM addresses such as 1FOO S1FFF might be used for data depending on the size of your program i e the number and size of your word definitions Another approach is to allocate memory for data within the dictionary the words CONSTANT VARIABLE and ALLOT described in the next chapter do this 4 9 1 Find Next Dictionary Location with HERE
302. tion mode The text from the input stream is subsequently executed See WORD STACK NOTATION DEFINITION GROUP ATTR COMPILE COMPILER bracket compile Used in a colon definition in form COMPILE lt name gt Forces compilation of the following word This allows compilation of an IMMEDIATE word when it would otherwise b xecuted COMPILER right bracket Sets the compilation mode The text from the input stream is subsequently compiled See NULL INPUT OUTPUT null Null is executed at the end of each line of input or p Screen of input It is not called directly by the user APPENDIX C T RSC FORTH ASS MBLER FUNCTIONAL SUMMARY This appendix contains a summary of the RSC FORTH Assembler word definitions grouped by area of primary function Consult appendix D for the detail definition of each word Stack Notation The stack operation is denoted in parenthesis The symbols on the left indicate the order in which input parameters must be placed on the stack prior to FORTH word execution Three dashes indicate the FORTH word execution point Any parameters left on the stack after execution are listed on the right The top of the stack is to the right Symbol Definition A
303. tions to save and restore return stack values see Section 7 4 and conditionals see Section 7 6 The END CODE word terminates a CODE definition in a similar manner as the terminates a FORTH colon definition During assembly of CODE definitions FORTH continues interpretation of each word encountered in the input stream not in the compile mode These assembler words specify operands address modes and op codes END CODE concludes the CODE definition An error check verifies correct completion then unsmudges the definition s name to make it available for dictionary searches 7 1 2 Assembly time Versus Run time It is important to understand at what time a particular word definition executes During assembly each assembler word interpreted executes Its function at that instant is called assembling or assembly time This function includes op code generation from mnemonics address calculation address mode selection and relative branch calculation The later execution of the generated code is called run time This distinction is particularly important with the conditionals At assembly time each word i e IF UNTIL BEGIN etc runs to produce machine code conditional branch and or jump instructions which will later execute at run time when its CODE definition name is used 7 1 3 CODE Definiti
304. to the data stack PUT Write two bytes to the data stack replacing the present top of the stack PUSHOA Push a zero and the accumulator to the data stack PUTOA Replace the top of the stack with a zero and the accumulator BINARY Combines the action of POPTWO and PUSH Our next example complements a byte in memory The bytes address is on the stack when NVERT CODE NVERT HEX TOP FF TOP POP END A new stack value may X tz EOR X JMP CODE stack by CODE ONE DEX DEX 1 LDA TOP STA TOP 1 STY NEXT JMP END CODE A simpler version CODE ONE 1 4 LDA PHA TYA PUSH END CODE JMP n LDA STA Change Replac is executed in Pp Code to put 1 on result from a COD EX E definition the stack Make room on the data stack Store low byte High byte stored from Y since Code to put 1 on the stack could use PUSH Code to invert a memory byte I O base to HI Fetch byte addressed by stack Complement accumulator memory Discard pointer from stack Return to NEXT We could place it on the zero Push low byte to machine stack High byte to accumulator Push to data stack 7 17 The convention for PUSH BINARY and PUT is Push the low byte on to the machine stack Leave the high byte i
305. tor is initialized to FB4A which points to COLD processing When FORTH is executing its inner interpreter i e NEXT it examines the interrupt request and inhibits bits of INTFLG When the interrupt inhibit bit 6 of INTFLG is ON the interrupt request bit 7 is ignored and NEXT xecutes the FORTH word When the interrupt inhibit is OFF the interrupt request bit 7 of INTFLG is tested If the interrupt request is OFF then NEXT xecutes the next FORTH word If the interrupt request is ON then NEXT passes execution to the word whose CFA is in NTVEC i e the interpretiv interrupt service word and sets the inhibit bit The interpretive interrupt word now processes the service required without interruption inhibit bit is set When the interpretive interrupt word has finished it must reset the inhibit bit to zero restore the interrupted word to the interpretive pointer and jump to NEXT to continue the interrupted execution Remember to keep the assembly interrupt code as short and simple as possible For example if you are reading data values at specific times 8 6 read them and put them away in say a FORTH variable using a small interrupt routine for just that purpose Meanwhile a high level FORTH routine examines that variable for new data and processes it when it appears FORTH is fast enough for much of the work to be done in high level which will sp
306. ts ON character for XON XOFF protocol Emits OFF character for XON XOFF protocol Stop interpretation Force compilation of IMMEDIATE word Compile a number into a literal Compile a double number into a literal Execute the definition CFA on top of stack Suspend compilation enter execution Resume compilation Forces execution when compiling The Text Interpreter executes or compiles User variable containing compilation state Create a dictionary header FORGET all definitions from lt name gt Returns address of next unused byte in the dictionary Leave a gap of n bytes in the dictionary A dictionary marker null word Find the PFA of lt name gt in the dictionary Search dictionary for lt name gt A 11 DICTIONARY CONTROL Continued PAD LATEST SMUDGI GI AUTOSTART TRAVERSE 2 KERNEL 756 HWORD NFA PFAPTR LFA pies 1 ness a e addr pawi addr pass deeem addr addr lt name gt addr n addr name addr cse pfaptr nfa nfa pfaptr pfaptr Ifa A 12 DEFINING WORDS name VARIABLE Compilation n name Execution name addr Compiles byte into dictionary Compile a n
307. ues below 84 54 and particularly above 96 60 may cause conflict with other system user variables PAD or the Terminal Input Buffer s Appendix G Be sure that your assignment allows one word two bytes for each user variable 4 10 5 ALLOT FORTH programs can use arrays records virtual arrays if mass storage is available and other data structures The most elegant way to create such structures is described in the chapter on user defined data types But a simple method which is sometimes good enough uses VARIABLE and another word ALLOT ALLOT takes one argument from the stack and leaves space for that many bytes in the dictionary For example O VARIABLE RECORD creates a variable called RECORD two bytes are available for the value Suppose 100 bytes are needed Then 0 VARIABLE RECORD 98 ALLOT would create the variable RECORD and leave the 98 extra bytes for it Suppose RECORD were to be used for a customer name and address the programmer could create such operations as LAST NAME 0 FIRST NAME 20 MIDDLE INITIAL 30 ADDRESS1 31 ADDRESS2 51 Then RECORD FIRST NAM E would return the address of the start of the FIRST NAME field In a similar manner arrays can be generated and manip of 300 bytes use 0 VARIABLE
308. um n3 n addr MEMORY plus store Adds n to the 16 bit value at the address by the convention given for Hj 12 213 ARITHMETIC plus minus Applies the sign of n2 to nl which is left as n3 addrl addr2 flag MASS plus buf Advances the virtual storage buffer address addr1 to the next buffer address addr2 Boolean flag is false when addr2 is the buffer presently pointed to by variable PREV nl run time CONTROL IC addr n2 compile time plus loop Used in a colon definition in the form DO nl LOOP At run time LOOP selectively controls branching back to the corresponding DO based on nl the loop index and the loop limit The signed increment nl is added to the index and the total compared to the limit The branch back to DO occurs until the new index is equal to or greater than the limit nl gt 0 or until the new index is equal to or less than the limit nl 0 Upon exiting the loop the parameters are discarded and execution continues Index and limit are signed integers in the range lt 327 168 032 T7612 WORD LOOP Cont BCD DUP STACK NOTATION DEFINITION GROUP ATTR At compile time LOOP compiles the run time word LOOP and computes the branch offset from HERE to the address left on the stack by DO n2 is used for compile time error checking
309. umber into the dictionary Pointer to temporary buffer Leave name field address NFA of top word in CURRENT Toggle name SMUDGE bit Returns address of next unused byte in heads dictionary or codes dictionary Leave a gap of n bytes in the heads dictionary or codes dictionary Compile a number into the heads dictionary or codes dictionary User variable containing headerless code flag If equal to one above words use code dictionary if not use heads dictionary Prepare autostart vector at addr which will cause name to be executed upon reset Note addr must be on a 1K byte boundary Adjust addr positively or negatively until contents of addr is greater then 7F Checks name to see if code is in kernel Display IN or OUT accordingly Separates heads and codes portions of definition to different place in memory Moves codes portion of last defined word from the codes memory to the heads memory Alter parameter field pointer address to name field address Alter name field address to parameter field pointer address Alter parameter field pointer address to link field address Begin colon definition of name End colon definition Create a variable named name with initial value n returns address when executed A 12 DEFINING WORDS Continued CONSTANT Compilation Cre
310. vailable for general use Its name is C CON It is used in the same format as CONSTANT For example 12 C CON TWELVE causes a new system address constant to be added to the vocabulary Unless you are working with special cases of target compiled code C CON has no advantage over CONSTANT It should be noted that C CON uses only byte values which limits its use to zero page addresses 6 2 2 Selecting Words with CASE LH The other new defining word of RSC FORTH is very useful There are many instances when a program needs to perform one of several actions based on a known condition For instance programs are often required to perform one of Several possible functions when an operator pushes a key The defining word CASE allows a very compact structure to be easily constructed When a word defined with CASE is executed a number is taken from the stack and is used to pick that numbered word from the definition and execute it 6 2 To illustrate the use of already defined CASE DOWN GI UP L BET a assume that several possible functions are R IGHT TO case structure could be built by defining as follows CASE Assuming causes an upward movement using LEFT coded key to left MOV MOV E LOOP movements up A word of caution when using a error checking on the entries made into the list last example would in all undesired
311. wher HEAD ERLESS is ly by selectively target a limited vocabulary can be f compilation A system Boolean value determining if the words HEADERLESS is zero normal a one codes are generated and heads in another accessible by EADERL ESS is not re location where the heads are generated XXXX quired The word H C forces a Boolean one into upplied number from the stack to be the memory It then displays the address is the address of heads dictionary and 6 4 CODES YYYY on the next line where YYYY is the address codes dictionary XXXX is the same as the operator supplied number and is displayed for verification YYYY is the value of DP at the time H C is executed In effect using H C creates two dictionaries one for heads and one for the codes With such an arrangement additional dictionary control words are needed to access both memory files The words DP HERE ALLOT and are sufficient for normal FORTH code Their counterparts added for headerless code dictionary control are DP HERE ALLOT and When HEADERLESS is a zero these words have exactly the same effect as their counterparts When HEADERLESS is a one these words work on the heads dictionary instead To test th ffects of the above words try the following examples First after reset run a short VLIST
312. y RSC FORTH operations such as Performing simple arithmetic and comparisons Using the stack Entering and retrieving data from memory Compiling interactively or in a batch mode from memory Defining new FORTH words Performing looping and conditional sequences A major portion of FORTH is the FORTH dictionary itself Each word in the FORTH dictionary causes specific actions or operations to be performed The use of FORTH is explained primarily by describing how each word operates and how to use it either individually or with other words the FORTH dictionary Let s start by seeing what is in List the contents of the FORTH dictionary by running a VLIST Type VLIST and then press the RETURN key The entire FORTH dictionary will be displayed Terminate the listing at any time by pressing any key The entire VLIST is shown in Figure 4 1 Note that the words do n ot appear to be in any general order the words are listed by their address in the R65FR1 Development ROM The FORTH dictionary structure is explained in detail in later These FORTH words are described in ASC sort order for convenient lookup in the glossary in Appendix B and summarized by associated function in Appendix A RSC FORTH may be readil Ly learn the accompanying exampl glossary Repeat the examples thoroughly understand the operation les Then read the word definition in the Appendix
313. y be read any time by executing a read at location 0019 for the Upper Counter A and at location 001A or location 0018 for the Lower Counter A A read at location 0018 also clears the Counter A Underflow Flag IFR4 The 16 bit latch contains the counter initialization value and can be loaded at any time by executing a write to the Upper Latch A at location 0019 and the Lower Latch A at location 0018 In either case the contents of the accumulator are copied into the applicable latch register Counter A can be started at any time be writing to address 001A The contents of the accumulator will be copied into the Upper Latch A before the contents of the 16 bit latch are transferred to Counter A Counter A is set to the latch value whenever Counter A underflows When Counter A decrements from 0000 the next counter value will be the latch value not FFFF and the Counter A Underflow Flag IFR4 will be set to a 1 This bit may be cleared by reading the Lower Counter A at location 0018 by writing to addre 001 A or by RES ss location Counter A operates in any of four modes Thes modes ar selected by the Counter A Mode Control bits in the Control Register See Table 9 5 The clock counter modes Table 9 5 Counter A Control Bits MCRL MCRO bit 1 bit 0 O O Mode Interval Timer Pulse Generation Event Counter Pulse Width Measurement
314. y code END CODE where the FORTH words are run at compile time and the assembly code is executed at run time When name is used later to define new words this assembly code address will be put into the code sequence of the new words Thus the new words will cause this assembly code to be executed For example GI VALU CODI 0 X LDA PUSHOA UMP END COD CREATE SMUDGE C A AG When used by typing 80 VALUE EIGHTY the word EIGHTY is created which when executed with a dot to print the stack top EIGHTY will yield 80 OK This page is intentionally left blank HANDI 8 1 TYPES OF INTERRUPT HANDLI level or interpretive interr SECTION 8 NG IN H ERRUPTS IN FORTH ERS Interrupts can easily be handled in FORTH using one of two methods machine upt processing A machine level or conventional interrupt handler is written in assembly language and performs the entire interrupt processing before returning to the interrupted routine NMI interrupts must be serviced with a machine level interrupt handler as shown in The IRQ interrupts can also be serviced with a the flowchart in Figure 8 1 machine level interrupt handler The general flowchart for using this method on the R65F11 R65F12 microcomputer is shown in Figure 8 2 This app
315. ype T 4 Press RETURN For example 16 05 00 SPACE T RETURN OK D Key C Key Causes the message and time to be displayed once each time D is typed The display format is lt MESSAGE gt HH MM SS The time is displayed immediately after the message for example D lt RETURN gt RSC FORTH TIME 16 05 10 The system remains in the FORTH command mode Causes the message and time to be continuously displayed For example C lt RETURN gt RSC FORTH TIME 16 05 30 Press a key to terminate the display although the clock will continue to run The key will also be interpreted as a FORTH command or data character 24 HOUR CLOCK US HEX C CONSTA E 1 1 4F C3 0 0 VARIABL VARIABL CONSTA CONSTA NG IRQ INTERRUPTS P H RIODL CONSTA ASSEMBLER P DISABLE PHA CLC 5 4 LDA 64 TICKS 3 TICKS 3 CMP CS TE 0 DL TICKS 3 TICKS 2 LDA CKS 2 50 ADC STA AT gt 1 STA INC LDA 3C CMP CS IF O LDA TICKS 2 TICKS cr TICKS 1 gt DAY3 2 BYTES TICKS 4 BYTES 0 RIODH S DISABLE USER VIA INT I SAVE IRQ VECTOR MS 100 00 60 STA INC LDA
316. ytes of RAM you can run quite large programs in FORTH by dividing the program into convenient The techniques for using program sized pieces and using program overlays overlays ar words FORGET like the disk data storage quite straightforward and LOAD to overlay programs Suppose you have a program that consists of three parts output time First construct what is called a 1 loading and executing the entire program part of the program is in screens processing part is in screens 30 12 13 screens 33 to 35 screen 102 and 103 of the program The resultin 31 and load screen Use the FORTH processing and If these three parts do not need to be resident in RAM all at the same they can be loaded and run sequentially which contains the directions for Suppose the source code of the input and 14 32 the source code for the and the output source code is in Further suppose that some data manipulating words are in CLEANS D CT ONARY DATA WORDS 13 LOAD 14 LOAD D 31 LOAD 32 LOAD 33 LOAD 34 LOAD 35 FORGET TASK TASK 102 LOAD 103 LOAD INPUT 12 LOAD PROCESS 30 LOA OUTPUT LEVEL INPUT FORGET L EV EL Each of the three overlay programs have the phrase LEV in the first screen to be loaded makes room in the dictionary for the next overlay started by in

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