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MPE IRTC Forth for the ATMEL AVR series

1. UNTIL 11 13 15 W NADAM 000 0 Licence terms 10 11 12 13 14 15 BEGIN WHILE REPEAT CASE OF ENDOF ENDCASE FOR NEXT DO LOOP Conditional Tests Seeing is believing Controlling a Port Comments Displaying Comments Loading a File Vocabularies CREATE DOES gt Demo Application Loading the Demo Running the Demo Viewing the Demo Inside the AVR TLM Forth Inside Forth NEXT NEST EXIT Data Stack Code and Variable Space Meta Compiling and the TLM Meta Compiling Unresolved References Remote Target TLM Library Number Conversion Multi tasking USER Area Running Tasks Semaphores Pipes Host Programs Exceptions CATCH and THROW Turnkey Operation AVR Assembler Introduction Conditional Flags Register Use Macros PUSH and POP Addressing modes Register Syntax Immediate 29 29 29 30 31 31 33 33 33 34 35 37 39 41 43 16 17 18 19 Register Direct Data Indirect Data Indirect with Displacement Data Indirect Post Increment Data Indirect Pre Decrement Direct Bit Data Direct Code Memory Indirect Direct Program Indirect Program Addressing Relative Program Addressing New Conditional Opcodes Code Definitions In Line Code CODE Stubs Interrupts Dumps Register File Dump VO File Dump Data Memory Dump E2PROM Memory Dump Interactive Serial Programmer Circuit Header Signal Connector 5 5 way
2. counterparts are SET BITS RES BITS and TEST BITS ON S m fa takes an 8 bit mask and address and sets all the bits set in the mask high at the address leaving the rest unchanged OFF S m fa takes an 8 bit mask and address and clears all the bits set in the mask low at the address leaving the rest unchanged CHECK S m fa m returns the logical AND of the 8 bit mask and the contents of the address These are only 8 bit functions and operate on any file address They may be used to manipulate flags registers or ports producing tight code Maths UM UM MOD 18 S s1 s2 s3 adds the top two stack items leaving the result on top of the stack Quick Forth Guide S s1 s2 s3 subtracts the top stack item from the second leaving the result on top of the stack UM S sl s2 s3 s4 multiplies the top two stack items to leave a double result on top of the stack i e 8 8 16 16 16 32 bits UM MOD S sl s2 s3 s4 s5 divides the double value under the top stack item by the top stack item leaving two values remainder second and quotient on top i e 16 8 8 8 32 16 16 16 bits Increment and Decrement 1 2 1 2 2 2 1 S sl s2 increments the top stack item by one 2 S sl s2 increments the top stack item by two 1 S s1 s2 decrements the top stack item by one 2 S sl s2 decrements the top stack item by two 2 S s1 s2 arithmetic left shift of the top stack item by one 2
3. the INI file to reflect the properties of the AVR device chosen Once loaded it is NOT possible to change the AVR type selection without restarting IRTC with another INI file New AVR xxxx INI files may be produced to specify new devices as they become available Existing INI files may be used as a template to produce your own Loading your AVR with a TLM IRTC runs the ISP in two modes Programming and Interactive Communication The serial programming mode is as described in the Atmel databook the interactive communications uses the same pins MISO MOST and serial communication at the ISP baud rate 38400 baud For the interactive mode to operate a small program the Target Link Monitor must first be programmed into the AVR Flash code space An image of this is created by xxx INI at load time and this must first be programmed into your device before development may begin You may program the TLM with REPROGRAM The ISP and Target must be powered and connected to a selected serial port No external connection except the ISP should be made to the Reset pin on the Target device or to the MISO MOSI and SCK pins REPROGRAM erases 5 Overview the AVR Flash before programming the code image from 0000 to HERE the end of the image When successful the AVR will now be ready for development Host and Remote modes When the compiler is running it is in one of two modes Host or Remote Host mode is used when you wish to use the
4. 46 AVR Assembler Jumps directly to PAUSE The is used in Forth to find the CFA of the following word If the word was created by a LABEL the is not required CALL STOP calls the subroutine STOP Indirect Program Addressing The program execution is continued at the address contained in Z Examples IJMP Jumps to the address in Z ICALL Calls the address in Z Relative Program Addressing The offset 2048 to 2047 is held in the instruction causing the execution to continue from the Program Counter plus the signed offset Example RJMP TEST Jumps to TEST relative RCALL TEST Calls TEST relative New Conditional Opcodes The AVR instruction set has four skip instructions for bit testing in the register and I O space New opcodes have been created to make use of these to reduce code and increase speed in conditional assembly The new opcodes are IF BRS Skips one instruction if bit in register set IF BRC Skips one instruction if bit in register clear IF BIS Skips one instruction if bit in VO set IF BIC Skips one instruction if bit in I O clear SBAK Skips back one instruction The IF instructions are combined with ELSE and THEN to create conditional assembly They may also be used instead of WHILE in a BEGIN WHILE REPEAT structure The SBAK may be used to create a fast loop waiting for a bit to set or clear See OUT in the AVRPROG3 file Code Definitions To defin
5. 5000C CONSTANT EXT INTS 000E CONSTANT EXT INT6 0010 CONSTANT EXT INT7 0012 CONSTANT TIM2 COMP 0014 CONSTANT TIM2 OVF 0016 CONSTANT TIM1 CAPT 0018 CONSTANT TIM1 COMPA S001A CONSTANT TIM1 COMPB 001C CONSTANT TIM1 OVF S001E CONSTANT TIMO COMP 0020 CONSTANT TIMO OVF 0022 CONSTANT SPI STC 0024 CONSTANT UART RXC 0026 CONSTANT UART DRE 0028 CONSTANT UART TXC 5002A CONSTANT ADC INT 002C CONSTANT EE RDY 002E CONSTANT ANA COMP multi tasking if GET MTMEGA Multi tasking taker else GET STMEGA Single tasking taker then FORTH PAGED DOWNLOAD IS DOWNLOAD H MEGA S Megal03 11 Target Configuration files 12 FORTH MEGA IS AVR TYPE IN META HOST STATISTICS CR CR IRTC for Megal03 Running in HOST mode The start and end of the file space code space and EEPROM space are set These are used to warn if exceeded during compilation The programming algorithm is set for a paged Flash device and the TLM object code is loaded into the PC Target image The baud rate for the TLM may be modified in the talker startup code but this must be done along with a similar modification to the ISP code if the baud rate value is to be changed Optimisation Optimisation By default the IRTC compiler creates subroutine threaded code with optimisation The following directives can be used to control the optimiser FAST CODE enable optimiser COMPACT CODE disable optimisier T As
6. CREATE to construct lists of values in the code space with C T and T which are words the compiler uses to store bytes and words into the code space When the table name is later executed it leaves a 16 bit address on top of the stack that points to the beginning of the list MC and M may then use this address to return the stored values Note The address used by MC and M is a byte address not a word address CREATE leaves a word address and this must be doubled CREATE 7 SEG DIGITS S a 0 3F C T 1 06 C T 2 5B C T 3 4F C T 4 66 C T 5 6D C T 6 7D C T 7 07 C T 8 7F C T 9 6F C T GET DIGIT S b b 7 SEG DIGITS 2 MC Here the table returns an address which is doubled by 2 and added to the offset of the digit required by MC uses the new byte address to fetch the value to the stack Logical Operators AND OR XOR NOT In embedded controllers the need for logical operators is paramount for the bit control necessary AND S s1 s2 s3 creates the logical AND of the top two stack items OR S s1 s2 s3 creates the logical OR of the top two stack items XOR S s1 s2 s3 creates the logical XOR of the top two stack items INVERT S s1 s1 inverts all the bits of the top stack item The code produced is in line and optimised Bit Control ON OFF CHECK These are TRANSITIONal definitions that do not appear in the Library Their Library
7. Checking the fuses Signatures Commands Object Save and Load External Programmers Errors Address NOT in the ROM Address NOT in the File Address NOT in the E2PROM Already aGOTO Already Resolved Conditionals Wrong Definition out of range Not enough Parameters NOT Erased NOT Compiling NOT an 8 bit number NOT in Remote NOT Resolved is NOT a Library Definition is NOT yet Defined or is In Line Could NOT enter Program Mode Prog Error Unresolved Word s Error lt word gt is undefined Licence terms 51 55 57 59 Licence terms vi 20 Suggested Reading 21 Further Information 61 63 1 Introduction Introduction Introduction Welcome to the world of the Interactive Remote Target Compiler IRTC and the Target Link Monitor TLM for the ATMEL AVR series of processors This package is optimised for use with the RAM Technology In System programmer ISP which is supplied as part of the package These products are designed to give fast and efficient turn round of ATMEL AVR based microcomputer products written in ANS Forth IRTC is simple to use but very powerful It is fast in compilation and allows good product documentation from the keyboard without the need for large manuals For those not familiar with Forth we would advise you start with one of the books in the Appendix Via the TLM and ISP IRTC provides a seamless integration of the Host PC and the Target hardware This
8. SECL Y If you wish to manipulate the stack you should do so with these macros If you write in line code and use these macros the optimiser will try to elliminate unnecessary stack use Addressing modes The AVR has many and varied addressing modes By no means all are used in the TLM but many are To understand their use it is strongly recommended that you read the ATMEL data book for a full explanation Here we will consider the addressing mnemonic used in the IRTC assembler Register Syntax 44 The same syntax that appears in the ATMEL data book has been used for register identification A upper case R for a register 0 31 and a upper case P for a I O register 0 63 Register pairs are indicated by RR and only apply to R24 26 28 and 30 For convenience and improved readability the registers register pairs and I O registers are pre defined R4 X Z Y Z BITO and SREG etc These may all be constructed but with Forth space delimited format e g 4 R 26 RR O BIT 63 P The pre defined versions are much more readable Also all the I O registers and the flags within them are predefined by name e g SIB UCR RXEN Will enable the UART reciever Note When using the I O Registers in a high level definition they must be preceeded by I O e g AVR Assembler 51 I O PORTB C Note When using the Register flags in a high level definition they must be preceeded by FLAG to generate a mask e g FLAG CS00
9. automate the interactive command line testing The TLM is a slave to IRTC and as such we may send a sequence of operations to it provided each will execute before a communication timeout occurs If we wish to test the Target hardware before embarking on the software we may set port bits and read port bits from Host programs e g ONLY META DEFINITIONS ALSO FORTH ALSO As TEST Sy 01 1 0 DDRA TARGET C BEGIN 10 MS 1 I O PORTA TARGET 10 MS SFE I O PORTA TARGET KEY UNTIL KEY DROP IN META This routine will toggle PORTA bit 0 approximately every 10 milliseconds until a key is pressed on the Host PC TARGET is required to compile the Host address of C as this is a Target definition The TEST word above only exists in the Host It uses the code in the TLM to operate but does not add any extra It is possible to incorporate Target definitions with the Host ones and then refer to them from within the Host words The Host program should be compiled in and run from the Remote mode after communication with the ISP is established 37 13 Exceptions CATCH and THROW Exceptions CATCH and THROW Like many high level languages Forth does not have an explicit GOTO This means that it is often necessary to create proprietary solutions to errors that occur in running embedded code To help with this the CATCH and THROW words have been added to the AVR Forth to assist with error conditions C
10. comments Displaying Comments if you wish to print out a remark or comment while a file is being interpreted or compiled use CR Comment string This will issue a Return and then print out the string on the Host terminal Loading a File 22 Once a file has been edited it may be compiled to produce the AVR runtime code with FLOAD lt filename gt INCLUDE lt filename gt GET lt filename gt If the file has a FTH extension the default no extension need be added to lt filename gt FLOAD scans the file from beginning to end and interprets the contents from the dictionary If you are in the Host mode the Target image only is updated If in Remote the code is also programmed into the AVR for immediate execution Quick Forth Guide INCLUDE and GET are aliases for FLOAD and may be used instead if you prefer This reads better when used to load include a file from within a file Vocabularies The Forth dictionary is divided up into sections called vocabularies Each contains words that are related and this subdivision means that only a part of the dictionary need be searched to find a function The Forth word ORDER shows a list of vocabularies that represent the current search order The one at the top of the list highlighted is called the CURRENT vocabulary and is the one that new definitions will be entered into The list below starts with the CONTEXT vocabulary which is the first one to be searched to find a wo
11. create a forward reference for now that will be resolved later This entire process continues until no more unresolved references exist in the TARGET vocabulary that have equivalents in the Library As Library words may contain other Library words it is necessary that no forward references exist in the Library The compiler will give an exception to any word it finds that has not been previously defined You may add to the Library both assembler and Forth definitions These are defined as follows High Level L lt name gt wordl word2 word3 EXIT L Code L lt name gt M ADIW TOS 2 INC TOSL PUSHT RET M L In the High Level definition word1 2 and 3 must exist in the Library prior to compiling this new definition M and M must start and end any code fragments Note High Level code must end with the EXIT and Code Routines end with RET or a JMP to code ending in RET Also If you wish to use a Forth word from the Nucleus like BRANCH BRANCH PAUSE STOP STATUS BASE PTR or PAD these must be preceded by TARGET in the Library definition This is because they do not have a Library version Also any fixed value must be followed by LITERAL or DLITERAL to give the correct compilation Number Conversion The AVR Library contains the fundamentals of number conversion That is ASCII string to a number on the stack and a number on the stack to an ASCII string 31 Library 32 The strings ar
12. how we might look at the problem in Basic In Forth we would write 12 3 0k Here the values are put first and the operator last This is called post fix or Reverse Polish Notation RPN we normally use pre fix The word outputs the top stack item converted to an ASCII number string to the PC screen The advantage to the computer is that it can only handle postfix order as it does everything sequentially It must have the values before it can do the addition In Forth the entry of the two numbers pushes them onto the stack The 2 was last so it is on the top of the stack with the 1 underneath it When Forth executes the code it only knows that it must add the top two stack values together and leave the answer on top of the stack The code does not need a location for the two numbers it just uses whatever is on the stack If we performed 1 2 5 gt 5 2 0kK The answer of 2 would be left on top of the stack No intermediate storage of the 1 2 is required This requires less memory and is dynamic with no need to garbage collect as there is no garbage Stack Nomenclature and Documentation 16 All Forth functions operate with the stack for parameter passing Any number of stack values may be input and output from a definition so we show the stack use of a word when we define it To do this and S are used as stack comments S nl n2 n3 nl n2 n3 Would mean that two values were required on entry
13. provides for the interactive testing of programs and hardware from the PC keyboard Test routines may be compiled and immediately run in the Target Memory may be viewed variables modified and the source code or help of any compiled word displayed As a consequence of the low cost of the IRTC and TLM we regret that is not possible to offer a voice Technical Hot Line We are however able to offer e mail for your enquires These will be dealt with as soon as possible Our E mail is tech support mpeltd demon co uk Web Page http www mpeltd demon co uk Installation and Configuration 2 Installation and Configuration System Requirements IBM PC with Windows95 98 or NT 16MbofRAM COMI Serial Port Hard Disk Mouse ISP Programmer supplied Target system 5V power source of at least 50 mA capability to power the ISP serial programmer The ISP must be connected to a serial port before running IRTC Hard Disk Installation Place the IRTC CD in the CD drive and run the Setup The setup wizard will install the software on to your hard drive in the directory of your choice The default is C XAVR The compiler and tools are run from the MPE development shell AIDE Make a short cut to AIDE on your desktop Configuration Run AIDE from the file AIDE EXE in XAVR AIDE There is a separate manual for AIDE In IDE gt MacroManagement set the AVRBASE macro to C XAVR or the directory where you have put the sys
14. registers from 0 to 63 Data Memory Dump The Data memory may be dumped by FDUMP As the registers and I O are also in the Data Memory you may use this to do part of the dumps shown by REG DUMP and IO DUMP E2PROM Memory Dump The data in the E2PROM may be dumped using EEDUMP 49 16 Circuit Interactive Serial Programmer Interactive Serial Programmer d eNv JL3lL 2665 Tur mdg AGR inu sa_ Hya 07 Lati af OA The IRTC ISP is similar to the Atmel serial programmer explained in their application note However a tri state buffer has been added to the IRTC ISP to enable the programmer to be used for both programming and development The control codes are the same as in the Atmel application note with the exception of Z This leaves the ISP in the program mode but tri states the SCK MOSI and MISO lines and sets RESET high to enable the target CPU to run stand alone The DTR line on the serial port controls the ISP operation switching between program and development mode In the program mode the 9052313 on the programmer accepts ASCII commands to control the program functions These functions are the same as the Atmel ISP In the development mode the 2313 is switched off and the buffers enabled allowing the Rx and Tx signals to pass through to the MOSI and MISO lines The TLM receives the serial data and enables development 51 Interactive Serial Programmer Header Signal Connector 5 5 way The ISP is powered fr
15. resultant code This may be done with HEX SAVE The start and end addresses are calculated and given to HEX SAVE with a filename The file extension HEX is automatically appended to the filename Use 0000 SOFFF HEX SAVE APPL The code is saved in the INTELLEC format and may be copied to a programmer Saved code may be re loaded into the Host Target image with HEX LOAD Again no file extension is required A is shown for every 1k of code loaded and a checksum of the code is given at the end Note The addresses used by HEX LOAD and HEX SAVE are byte addresses not word To save your total application use 0 HERE T HEX SAVE APPL Also the word CODE FILE will create a HEX file called with the code range 0 to HERE T This may be viewed by the Atmel Studio debugger AvrDebug exe The word SEE will try to find the following word in the Target and if compiled shows the CFA of the word creates CODETEST and runs AvrDebug For this to work it is necessary to copy AvrDebug exe into the COMPILER directory 55 18 External Programmers External Programmers There are three methods of transferring code to an EPROM programmer for Production code generation From within IRTC two words BIN gt PROG and HEX gt PROG allow a binary or an ASCII Hex download via COMI Both these require the code start address and end address COMMS 1 8 NONE 9600 BAUD 0000 03FF BIN gt PROG 0000 03FF HEX gt PROG The
16. the compiler generates machine code it is possible for it to scan the code as it is compiled and to optimise the result This process operates in a single pass so the optimisation is limited but is very useful Forth requires parameters on the stack before executing the function If these parameters are literals it is often possible to reduce the code e g TST 03 PORTA C This would require the following code PUSHT X Make room LDI TOSL 03 literal 03 LDI TOSH 0 PUSHT Make room LDI TOSL PORTA literal PORTA LDI TOSH 0 CALL C CALL C routine RET finished However the optimizer produces LDI SECL 03 literal 03 STS PORTA SECL Store to portA RET finished This has saved 6 words of storage and several micro seconds of execution time It would be unusual to make this simple code a definition and so this would normally become in line code within a larger definition Also in this example if the literal 03 was computed at run time the result is already in TOS so the compiler just saves TOSL into PORTA and then cleans the stack 13 7 First words Interactive Quick Forth Guide Quick Forth Guide Good organisation and effective communication require us to e define and name useful tasks or operations e group these into larger related ones This is how Forth works It consists of a dictionary of words grouped into vocabularies Each word is an operation and words are de
17. time out of the pipe and sends it back to the Host The rate at which the characters come back is controlled by a Timer interrupt running every 111mSecs So you see the Target is quite busy The tasks LETTERS and NUMBERS are endless they just run and run UART only runs once and then STOPs The Timer interrupt AWAKENs UART and it runs once again So the characters occur at a 111mSec rate The funny thing is why do the letters and numbers that are being put in the same pipe not get jumbled up and why two sets of letters and only one of numbers with the CRLF after letters and not numbers The answers to these and other questions come later see Semaphores Saving a target image You can save the target image in image straight binary or Intel Hex format using SAVEIMG lt filename gt SAVEHEX lt filename gt Note that Intel Hex files can be loaded into the standard AVRDEBUG EXE program for disassembly and simulation Memory and AVR Registers 4 Memory and AVR Registers RAM Rara End Siacks E aria bles ectors LA Registers RAMi Start ROM R OMi End Application TL Pw Ree Sectors we ctors ROBI Start Separate Code and Data The AVR has separate code and data spaces The following words operate on DATA space ca C 24 2 FILL ERASE BLANK CMOVE ACQUIRE RELINQUISH But the code memory space uses Mc M T C T AVR Working Regis
18. to call each word used within a definition Each Forth word starts with a Every NEST must EXIT as every Jump to Subroutine must Return from Subroutine The value on top of the System Stack is popped by a RET instruction that is compiled by the at the end of each Forth word definition Data Stack Forth is a stack based language The Return Stack used for calls and returns has been described above The Data that is to be manipulated is placed on the Data Stack The processor s YREG is used to control this stack The TLM does however have an unusual feature The top Data Stack item is always in the XREG The Data Stack controlled by YREG Quick Forth Guide containing any items below this In a machine code definition the X and Y registers must be saved if they are required by the definition and restored if the definition itself does not affect the Data Stack This is most easily done by pushing out onto the Return Stack at the beginning of the definition For use by the tasks a USER location SPO is reserved for saving the Return Stack pointer the Data Stack pointer is saved on the Return Stack Code and Variable Space In an AVR embedded system the Code space is in Flash memory The Variables must therefore have a RAM area for their contents These two spaces are controlled by different words The Code space is set by ORG This is similar to the construct in assemblers Use 0060 ORG The address 0060 is set in AVR xxxx INI I
19. using WORD gt and C the Host may display the current Target stack contents When in the Remote mode S does this function With C the Host may modify AVR resources This allows you to write Host programs that require no further Target code but that will exercise hardware external to the AVR This is very useful in development and production to do initial testing Library 9 Library To make best use of the code space of the AVR we do not compile a Forth kernel with all the standard Forth words and then compile our application Instead we use a Library All the Forth definitions are compiled into the LIBRARY vocabulary and executed by the compiler as they are found in the input stream The definitions in the Library are special but the words L and L allow you to create your own functions to extend these definitions Library words are required to perform two differing functions depending on their use If a word is encountered when compiling a definition in the Target it is made into what is called a Forward reference if it has not been previously compiled When the compiler reaches the end of the current definition it tests the TARGET vocabulary for any such references These are then looked up in the LIBRARY vocabulary to see if they exist If so the Library definition is executed This will generate the Target code necessary and resolve the references If however the Library definition contains other Library words their execution must
20. 45 AVR Assembler Data Indirect Post Increment Here the destination or source addresses are given by the contents of a register pair X Y or Z which are then post incremented Example LD TOSH Y LD TOSL Y In IRTC Y contains the Data Stack pointer DP The above example is equivalent to a DROP Data Indirect Pre Decrement This is similar to Data Indirect with Post Increment except that the indirect register pair is decremented BEFORE the data is accessed Example DMR BZ Direct Bit In the Direct Bit addressing mode any bit in any register or I O can be addressed and potentially modified Examples SBR R7 BIT3 sets bit 3 in working register 7 CBI PORTC BIT4 clears bit4 in I O portc Data Direct This mode addresses the specific location within the data memory directly It only needs the absolute address value Example STS COUNTER R9 location COUNTER is loaded with the contents of the register 9 LDS R9 COUNTER R9 is loaded with the contents X of the data memory location COUNTER Code Memory Indirect This mode uses the Z register pair to hold the absolute code memory address Example LPM The code memory addressed by Z is loaded into RO only Note The address is the byte address the LSB specifies the high or low byte Direct Program The program execution continues at the address contained in the instruction Example JMP PAUSI E
21. ATCH The CATCH word takes a CFA from the data stack and executes it after first placing its position and the current stack depths onto the return stack The word HANDLER records the position of this stack frame for later use by THROW and its previous value is also saved to allow nested CATCH and THROW structures lt word gt CATCH ERROR CATCH allows a value to be returned to show the error condition If no errors are encountered lt word gt finishes normally and returns to after CATCH THROW When an error is encountered in the word run by CATCH a non zero value is placed on the data stack and THROW executed THROW takes the value in HANDLER and restores the stacks to where they were when CATCH was executed except for the addition of the non zero value given to THROW DUP IF THROW THEN HANDLER is a USER variable in multi tasking systems and so the error recovery may be used within each task 39 14 Turnkey Operation Turnkey Operation At some point in your application development it is necessary to run the code directly from Reset There are two ways this may be done Reset Vector Compile a JMP to your application at address 0000 EEPROM Vector Use RUN lt name gt to set the EEPROM start vector and run the code The first is the way that a final system should be compiled The second is useful in testing as the vector may be reset to FFFF with END RUN after the operation has been tested but without h
22. Binary has no checksum or address it is just a dump of the code at the addresses from the Target image in the Host Similarly the Hex is just a code dump again with no checksum or address transmitted Both give a checksum on the screen for the bytes sent for comparison with that generated manually in the programmer The last method is to use the INTELLEC file appl HEX This contains records with address and checksum To download this to the programmer MS DOS COPY may be used This may be from the command line of DOS or from within IRTC with SHELL COPY appl OBJ COM1 B lt cr gt The word SHELL may be used to send any combination of DOS commands from within IRTC SHELL alone will shell out returning via EXIT 57 Errors 19 Errors Address NOT in the ROM The dictionary pointer DP T has exceeded the value in ROM END Address NOT in the File The variable pointer VP T has exceeded the value in RAM END Address NOT in the E2PROM The E2PROM pointer has exceeded the value in EEPROM END Already a GOTO Compiler was converting a call to a goto and found it was already Already Resolved The word being resolved is already resolved Maybe a duplication Conditionals Wrong The compiler has detected that the conditionals are not matched An IF may not have a THEN or a value may have been left on the Host stack during compilation Definition out of range This only applies to devices with more than 2K of code spac
23. FGHIJ ABCDEFGHIJ 123456789 ABCDEFGHIJ ABCDEFGHIJ 123456789 ABCDEFGHIJ Done The screen should clear and the following appear forever The result is not too impressive but what is happening is quite interesting TTY is just a simple terminal emulator It accepts serial input and puts it on the screen There are three tasks described later that result in these characters appearing The first is called LETTERS sends the string ABCDEFGHIJ to a pipe See Pipes The second NUMBERS sends the converted number string 123456789 CRLF to the same pipe The third UART takes one character at a time out of the pipe and sends it back to the Host The rate at which the characters come back is controlled by a Timer interrupt running every 111mSecs So you see the Target is quite busy The tasks LETTERS and NUMBERS are endless they just run and run UART only runs once and then STOPs The Timer interrupt AWAKENs UART and it runs once again So the characters occur at a 11 1mSec rate The funny thing is why do the letters and numbers that are being put in the same pipe not get jumbled up and why two sets of letters and only one of numbers with the CRLF after letters and not numbers The answers to these and other questions come later see Semaphores 25 Quick Forth Guide Viewing the Demo To stop the demo press the ESC key on the PC Type REM cr lt Megal03 Stack Empty ok you should see something like this We now
24. I O TCCRO ON To differentiate between destination and source operands a space delimited comma is used e g ADIW TOS 2 BEWARE of the use of a Forth while in the assembler as very odd results will occur Immediate The operand value used by the instruction is the value supplied by the operand field itself The hashmark optional is used to distinguish data from an absolute address and may only be in the source field Examples LDI R26 04 Adds 4 to the value originally contained in register R26 SBIW TOS 3 Subtracts 3 from the top stack item Register Direct In this mode a register is be addressed by using its absolute address in the register file Example ROL R4 Rotates the contents of register number 4 left one bit Data Indirect In this mode the address of the data does not appear in the instruction but is located in a register pair X Y orZ Example LD TOSL X CLR TOSH This is equivalent to a C in Forth X being the top stack item holds the address of the data byte Data Indirect with Displacement The indirect working register acts as a base or starting value to which is added an immediate offset 0 63 to point to the data The offset value is the immediate value given in the instruction while the index value is given by the contents of a register pair Example LDD R10 Y 5 I Y contains 55 then the contents of 60 55 5 will be loaded into register 10
25. MPE IRTC Forth for the ATMEL AVR series User Manual MPE IRTC Forth for the ATMEL AVR series User Manual Manual revision 1 100 Date 22 September 1999 Software Software version 1 100 For technical support Please contact your supplier For further information MicroProcessor Engineering Limited 133 Hill Lane Southampton SO15 5AF UK Tel 44 0 2380 631441 Fax 44 0 2380 339691 e mail mpe mpeltd demon co uk tech support mpeltd demon co uk web www mpeltd demon co uk Acknowledgements The source code for this product was licensed from RAM Technology Limited It has been modied and enhanced for use on MPE s ProForth VFX for Windows which is the host Forth and for use with MPE s AIDE development environment MPE Forth 6 for the ATMEL AVR series Copyright O RAM Technology Limited MicroProcessor Engineering Limited 1998 1999 Licence terms Notice RAM Technology Systems and MicroProcessor Engineering MAKE NO WARRANTY OF ANY KIND WITH REGARD TO THIS MATERIAL INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE RAM Technology Systems shall not be liable for errors contained herein or for incidental consequential damages in connection with the furnishing performance or use of this material This document contains proprietary information which is protected by copyright All rights are reserved No part of this document may be
26. P OVER ROT DROP NIP TUCK As all the parameters are passed on the stack Forth has several words to manipulate the stack contents DUP S s1 s1 s1 will duplicate the top stack item leaving two identical values SWAP S s1 s2 s2 sl exchanges the top two stack items OVER S s1 s2 s1 s2 s1 copies the second stack item onto the top of the stack pushing down the first ROT S s1 s2 s3 s2 s3 s1 brings the third stack item to the top of the stack and the top and second are pushed down DROP S s1 removes the top stack item opposite to duplicate NIP S s1 s2 s2 removes the second stack item TUCK S sl s2 s2 sl s2 copies the top stack item beneath the second stack item These operators allow us to use the stack for local storage during words and re ordering the results to pass on to the next word Memory Operators ce C MC MQ 17 Quick Forth Guide The AVR has two memory areas to which it has access code and RAM C and C fetch from and store to a single 8 bit RAM location These two words are optimised during compilation if fixed values literals are used as the operands By using I O before an I O register C and C may be used to access the I O locations as though they are RAM The words and are 16 bit RAM operators All these use a 16 bit address to access the location The code space in the AVR is only accessible indirectly via the Z register and the LPM instruction Tables may be made using
27. PC and its resources without any communication with the Remote Target You may wish to perform some inspection of the Target image memory for example All references to Forth kernel words like etc will be from the Host definitions That is those definitions that relate to the 80X86 processor in the PC After you type REM Remote mode will be announced This indicates that where applicable IRTC will use the Remote Target for execution of the Target word definitions This means that you now have two Forth systems running together The Host controls everything through IRTC but execution occurs in the Remote Target When you type on the PC keyboard the Host parses your input and performs the necessary actions to instruct the Remote Target what to do The Target is a slave but does execute the run time code in real time This bit is for Forth techies and don t worry if you don t understand it yet The Vocabularies that will be searched are modified by the mode selection When in the Host mode the first two will be METAAVR This is the IRTC main vocabulary When in the Remote mode the first two will be METAAVR and TARGET The TARGET vocabulary holds all the AVR Forth definitions for the Remote Target This will be the first vocabulary searched so etc will now be the Remote versions in the AVR The following Forth words are useful for switching modes REM switches to REMOTE mode if not already there HOST switches to Host mode
28. REPROGRAM programs the target AVR with the code compiled so far This must be done before switching to Remote mode Once in Remote mode the compiler will automatically update the target memory VERIFY checks the target Flash image against the compiler s image STATISTICS tells you useful things such as how much of your code space has been used up Running the DEMO application Run AIDE Configure the macros and IDE as described earlier Click the AVR icon The compiler will run and when it finishes type REPROGRAM sets up the Flash REM switch to remote mode GO the main application word ignore the NO Ack Message TTY Start the simple terminal emulator press ESC to finish What you should see is ABCDEFGHIJ 123456789 ABCDEFGHIJ ABCDEFGHIJ 123456789 ABCDEFGHIJ Overview ABCDEFGHIJ 123456789 ABCDEFGHIJ ABCDEFGHIJ 123456789 ABCDEFGHIJ Done The screen should clear and the above appears and runs until you stop it by pressing the lt ESC gt key The result is not too impressive but what is happening is quite interesting TTY is just a Dumb Terminal It accepts serial input and puts it on the screen There are three tasks described later that result in these characters appearing The first is called LETTERS sends the string ABCDEFGHIJ to a pipe See Pipes The second NUMBERS sends the converted number string 123456789 CRLF to the same pipe The third UART takes one character at a
29. S s1 s2 arithmetic right shift of the top stack item by one Constants and Variables Often we require a value that is fixed and used throughout our application for example the bit on a port This may be compiled as a CONSTANT 2 CONSTANT PUMP IRTC will cause this to be compiled as an in line literal whenever the word PUMP is encountered If the COMPACT CODE directive is set a subroutine will be compiled immediately and all references will be via calls This may save code space but does not allow the optimiser to reduce code When the value required needs to be changed during execution a VARIABLE is defined VARIABLE COUNTER Here VARIABLE compiles an in line literal of the address of a 16 bit two byte location in the file These locations start at the address in RAM START and an error is generated if too many variables are declared resulting in the pointer going above the value in RAM END The variable allocation pointer is incremented automatically by each variable declaration The pointer may be set absolutely by VORG VARIABLE allots two bytes and CVARIABLE one byte and C may be used to access the contents and C to change the value Note The contents of a variable location are undefined at compile time It is necessary to initialise the contents at the start of your application if not implicitly done so by your code Control Structures The flow of control in a program is normally sequential control structure
30. Target related just executes in the Host PC and leaves its result there During Target CODE definitions all the Assembler words are executed The object code generated is placed in the Target image in the PC and sent to the ISP for storage in the Remote Target if in the Remote mode The execution of these words by the Host causing this result Unresolved References The statistics from our DEMO load displayed a line for Unresolved References when we ran STATISTICS None were shown for our demo as all the references words could be found 29 Meta Compiling and the TLM when compiling If this is not the case say because a word was incorrectly spelled the word name would appear under the Unresolved Reference heading IRTC differs from many Forth implementations in that forward references are allowed and are automatically resolved This applies to Forth kernel words as these are contained in the Library Any forward reference made in your application code will be resolved when the definition is compiled later from the source In IRTC it is therefore not usually necessary to explicitly define forward references although you may with FORWARD This is true for your Target application code only Library extensions do require special conditions for forward referencing and will cause compile exceptions if they occur Remote Target TLM 30 The Target Link Monitor is a small 712 byte program that allows the communication with the Host PC a
31. ails of multiple copy terms and site licensing As this copy is sold direct and through dealers and purchasing departments we cannot keep track of all our users If you fill out the registration form enclosed and send it back to us we will put you on our mailing list This way we will be able to keep you informed of updates and new extensions as they become available If you need technical support from us we will need these details in order to respond to you You will find the serial number of the system on the original issue discs Contents Licence terms Notice Distribution of application programs Warranties and support 1 Introduction Introduction 2 Installation and Configuration System Requirements Hard Disk Installation Configuration 3 Overview Selecting the right AVR CPU Loading your AVR with a TLM Host and Remote modes Running the DEMO application Saving a target image 4 Memory and AVR Registers RAM ROM Separate Code and Data AVR Working Registers 5 Target Configuration files 6 Optimisation 7 Quick Forth Guide First words Interactive The Stack Stack Nomenclature and Documentation AVR Forth Data Stack Size Return Stack Data Stack Operators Memory Operators Logical Operators AND OR XOR NOT Bit Control ON OFF CHECK Maths UM UM MOD Increment and Decrement 1 2 1 2 2 2 Constants and Variables Control Structures IF THEN IF ea ELSE vaca THEN BEGIN AGAIN BEGIN
32. and one value is left on exit from the word Operands of differing sizes and types are shown below nl n2 16 bit signed numbers dal d2 32 bit signed numbers ul u2 16 bit unsigned numbers al a2 16 bit addresses fal fa2 8 bit file addresses bl b2 8 bit bytes AVR Forth Quick Forth Guide cl c2 ASCII characters f 8 bit flag 0 false 255 true After the general discussion of Forth we may now look at the Forth implementation used for the AVR IRTC creates subroutine threaded code with optimisation if the FAST CODE directive is used Many Forth words are compiled as in line code to further improve execution speed Data Stack Size Return Stack The Forth Data stack size is 16 bits Eight bit byte values are represented as a 16 bit value with the upper 8 bits set to zero 32 bit double values are represented by two stack values the top value the most significant The top stack value is always in the TOSL TOSH registers R26 and 27 the X register The Y register R28 DPL and R29 DPH holds the pointer to the rest of the data stack Macros PUSHT and POPT push and pop the top stack item on and off the external stack Also R24 and R25 are used as a temporary second stack item SECL and SECH that has macros PUSHS and POPS The return stack for the Forth word calls is controlled by the stack pointer SPL and SPH in the AVR VO space The PUSH and POP mnemonics control the stack along with CALL and RET Data Stack Operators DUP SWA
33. are back to before running the demo We have loaded several new words the only one you have used of so far is GO IRTC can show you them all in two ways The first is to use the ForthEd editor in AIDE Type ED DEMO CTL cr The editor screen should appear with the contents of the file DEMO CTL displayed This is the so called control file for the demo program The DEMO CTL file does not give us much information about the program only the files that go to make it up So open another file to brose that one Inside the AVR TLM Forth 26 Forth has been used much more widely that many people think The reason that it is not recognised is that the applications are embedded into products This package it is hoped will continue this tradition Inside Forth NEXT NEST EXIT A detailed description of the TLM Forth is given here to assist those wishing to use code definitions in particular The so called Forth inner interpreter NEXT and the associated call NEST and return UNNEST definitions make up the Forth machine This is the heart of a Forth machine In a subroutine threaded Forth NEXT is a CALL instruction The return address is placed on the return stack by the processor the address called is called the Code Field Address CFA Every high level Forth word is a subroutine It is called and the CFA points to the code The IRTC compiler keeps track of the Forth words and compiles CALL or RCALL instructions
34. aving to REPROGRAM Also RUN lt name gt may be used to test an individual section of your code The word used by RUN would be compiled to set any variables ports etc and would then execute your code RUN places the address of this test routine into 01 02 of the EEPROM tri states the SCK MOSI and MISO pins from the programmed and Resets the Target CPU When reset the TLM initialises the Target and runs the test routine from the vector placed in the EEPROM The RUN command invites you to press the ESC key to exit This resets the EEPROM vector and does a REM to get back to interactive development Any other key will exit without resetting which will leave the code in a turnkey mode Any REM or reset will run the test code until the EEPROM vector is reset IS APPLICATION performs the same function as RUN but also creates a JMP to the application code address at code address 0000 lt application gt IS APPLICATION This should be placed at the end of your code to create a turnkey system NOTE It is necessary for the application code start to set up the MAIN TASK and Forth registers before running the high level code See MAIN in TLM NOTE It is possibe to get into a lock out situation 1f your test or application code uses the development UART port as with the muli tasking demo Here the ISP will not enter the program mode because there are characters being sent back by the running application To fix this use the following Select t
35. e A jump within an IF THEN BEGIN UNTIL etc is more than a relative jump Not enough Parameters The word being executed by the Host did not have enough parameters on the data stack to run NOT Erased The address shown is not 3FFF NOT Compiling The compiler is interpreting and should be compiling NOT an 8 bit number The value on the Host stack is greater than 255 NOT in Remote IRTC is not in the Remote mode and should be NOT Resolved The word is not yet resolved and still has forward references 59 Errors is NOT a Library Definition The word could not be found in the Library vocabulary is NOT yet Defined or is In Line The word does not have a header in the Target vocabulary so it may have been used but only produced in line code Could NOT enter Program Mode The ISP could not establish contact with the Target CPU Reset and try again Prog Error The ISP did not respond to the command properly Unresolved Word s Shows the words that are unresolved Error lt word gt is undefined The word could not be found in the current search order 60 20 Suggested Reading A range of Forth books is stocked by MicroProcessor Engineering Among them these are suitable introductory books Starting Forth Leo Brodie ISBN 0 13 842922 7 Object Oriented Forth Dick Pountain ISBN 0 12 563570 2 Thinking Forth Leo Brodie ISBN 0 13 917568 7 61 Further Informati
36. e a Forth code word the assembler must be invoked to allow the instruction words to be found Three words will do this CODE LABEL and INTERRUPT CODE creates a Header for the word following and causes the assembled machine code to be run when the word is executed This is just like a Forth definition only in code LABEL creates a Header for the following word that only leaves the address of the assembled machine code on the Host stack when the word is executed This is often used as a reference for jumps or branches within a CODE definition All assembler definitions must end with END CODE or C These words terminate the assembler and test the Host stack for irregularities CODE definitions will usually end with RET 47 AVR Assembler In Line Code CODE Stubs Interrupts 48 As AVR Forth is subroutine threaded and produces machine code it is possible to put code fragments into a high level definition The code is encompassed with C and C for example TEST C ADIW TOS 4 C This adds 4 to the item on top of the stack If you are only using assembler code you may still use TLM to test your routines TLM expects the CFA it receives to be that of a subroutine If you have used CODE definitions for your routines these may be executed by name from the command line If they are defined by LABELs then a stub is required e g CODE TST JMP lt name gt C This assumes lt name gt is a routine ending in a return
37. e held in an area called PAD This traditionally has been 64 bytes beyond the current end of the dictionary In embedded systems this is not practical for two reasons e Dictionary is in memory when running e Not re entrant for tasks To overcome these PAD has been defined as a USER variable It is 11 bytes above it s nearest partner PTR This is to allow for the number to ASCII string to be converted down from PAD the largest double number is 2 147 483 648 or 10 characters plus a sign makes 11 The string for conversion to a number is traditionally from PAD up so enough space above is also required The definitions in the Library are only the conversions NUMBER takes the address of an ASCII string and returns a double number and a true flag if sucessfull D takes a double number and returns the address and length of the converted string Both require the USER variable BASE to be loaded with the radix required for the conversion These are then used by application dependant code to input and output the strings These conversions are for double numbers you may use them as such dropping the top item for 16 bit or modify then for different applications 10 USER Area Multi tasking Multi tasking Multi tasking is a function that until recently was not so generally known The Forth community have been using it for many years indeed Charles Moore s first Forth s used it Once used you will wonder how you did without it The version i
38. e test e g 0 IF branch if non zero 0 NOT IF branch if zero The AVR register use is described in the TLM Forth section Here is a r sum of that usage YReg Data Stack Pointer XReg Top of the Data Stack SP Return Stack Pointer R22 23 UP Task Area R16 21 N ScratchFile Use Because of the way Forth and the Assembler work it is possible to define Macros for use in the assembly process If we make a Host definition which contains assembler words when interpreted at compile time the definition will execute these words This will place the assembler code directly into the Target An example of this technique is XASM DEFINITIONS MACRO PUSHT ST Yt TOSL ST Y TOSH MACRO 43 AVR Assembler IN META Using this technique it is possible to construct repetitive code for insertion in your machine code programs Note You may also produce the same result with an H definition and M Me g A PUSHT M ST Y TOSL ST Y TOSH M PUSH and POP Four other macros are pre compiled to assist with stack control PUSHT places the TOS contents onto the data stack with the following code ST Y y TOSI ST Y TOSH POPT gets the data stack into TOS whith the following LD TOSH Y LD TOSL Y PUSHS places the SEC contents onto the data stack with the following code ST Y SECL oT X y SECA POPS gets the data stack into TOS whith the following LD SECH Y LD
39. ea used by number conversion UP 34 Next available USER address Running Tasks The Task areas allocated by TASK which is preceded by three values to set the task data return and user stack areas Then we must chaine the tasks together at runtime To do this we LINK the tasks task name LINK The LINK process adds a task to the chain but sets the task as RESTing To make a task run the application we wish the USER area and the task s stacks must be set to run whatever word we select The task must be ACTIVATEd 33 Multi tasking Semaphores 34 task name ACTIVATE lt word gt This must be inside a definition lt word gt must be an endless loop or terminate with STOP To keep tasks synchronised we use semaphores These are global variables that are loaded with a unique value relating to the task that wishes to take control This value is the Task s USER area address A semaphore is initialised to zero At this point any task may take control When a task wishes a resource it ACQUIREs the semaphore From now on no other task may acquire this resource as the semaphore is non zero To allow others access the task it must RELINQUISH the resource and reset the semaphore This mechanism provides for simple inter task communication provided the tasks do not hog any given resource Tasks must co operate If you refer to GLOBAL FTH from our earlier demo you will see STREAM is used as a semaphore for the pipe l
40. embly subroutines Then words or subroutines are added to the TLM code to extend it into an application With the C file fetch and C file store routines added the TLM may test the hardware external to the AVR as we then have the capability to change any file space location ports and registers included The TLM may be seen as a server to the Host and programs may be written to exercise the Target hardware without any further AVR code being compiled This ability to test the hardware before any application specific software is written is one of the main advantages of IRTC Being Forth based this process is interactive with direct hardware operation from the command line XAVR EXE is the base compiler that incorporates IRTC and AVR generic facilities To produce an an application load a CPU specific INI file that defines processor specific features and then load the application code This is normally done by loading a file we call a control file usually with a CTL extension You can run XAVR EXE from the command line or a short cut XAVR EXE GET DEMO CTL However we recommend running it from the AIDE environment which gives additional useful features Selecting the right AVR CPU For AVR Target configuration in AVR xxxx INL see Target Configuration If your application is not going to use the Megal03 change the XAVR DEMO DEMO CTL file to select the correct INI file from the XAVR KERNEL directory IRTC is modified by
41. etween FOR and NEXT executed NEXT decrements the index and if true non zero returns to FOR If the index decrements to zero false it is removed from the Return Stack and the loop terminates DO LOOP Use limit index DO words LOOP DO transfers the 16 bit values of the loop limit and the start index to the Return Stack The words between DO and LOOP are executed at least once LOOP increments the index and tests it against the limit If the index is still less than the limit the loop executes again If not the Return Stack is cleared and the loop exits To leave the loop early use LEAVE This forces the index to be the same as the limit so that the loop will exit when LOOP is next run Conditional Tests 0 S s1 f the flag is true if the top stack item is zero O lt S sl f the flag is true if the top stack item is less than zero O gt S s1 f the flag is true if the top stack item is positive greater than zero S s1 s2 f the flag is true if the top two stack items are equal lt gt S s1 s2 f the flag is true if the top two stack items are not equal lt S sl s2 f the flag is true if sl is less than s2 gt S s1 s2 f the flag is true if sl is greater than s2 U lt S sl s2 f the flag is true if sl is logically less than s2 U gt S s1 s2 f the flag is true if sl is logically greater than s2 Seeing is believing As IRTC creates AVR machine code and optimises it as it goes it ma
42. fined in terms of those that went before This dictionary defines Forth itself and is added to by your application to grow into a new Forth that solves your problem Let us look at an example of how this works for a simple FAX machine send ring read transmit hang up The in Forth indicates the start of a new definition The space delimited text following will be the name of the next entry in the dictionary These names are called words in Forth The other words already exist in the dictionary and are the functions performed by this new definition The terminates the new dictionary addition This process is called compilation and the finding of the words in the dictionary interpretation The words ring read transmit and hang up are defined in terms of other words for example the word read Read BEGIN scan line page end UNTIL Here we see read defined in terms of other words this time with a looping structure that terminates at the page end Notice that the definitions are short and the word names relevant Also we have shown the definitions in a top down style which is how you might consider the problem but they would be implemented in a bottom up fashion This means that the simplest task is defined and tested first building up to the final function send The words in read may well consist of what are called Forth primitives as are the BEGIN UNTIL structure in read itself These primitives are the fundamental functions
43. get definition words go here together with any Library definitions used during compilation When changing from Host to Remote or back the vocabulary order is also changed This order is re established whenever the lt cr gt key is pressed If you change the order it will only last for one command line of input When entering CODE definitions from the command line each new line should start with XASM definitions may only be one line in length A list of words available in each vocabulary may be seen with lt vocabulary name gt WORDS 23 Quick Forth Guide CREATE DOES gt This construct is what makes Forth somewhat unique It allows the compiler to be extended In fact the assembler is written using this construct to define words that will create others of the same mould Let us explain by example H CONSTANT CREATE T DOES gt The H tells the Host that this definition is for it and not the Target All the words between H and DOES gt will be compiled into the Host as a Host definition All the words after DOES gt will be Target words defined in the Target So what are we doing guru warning CONSTANT is the new name that we are adding to our compiler CREATE will create a header in the Host when CONSTANT is run at Target compile time The word T will save any value on the Host stack into the next available space in the Target dictionary when CONSTANT is executed DOES gt will terminate the H
44. he HOST mode Ctrl Shift H Type DESELECT Type TTY any characters in the buffer will be displayed and the ENTER key should produce a Exit TTY with the Esc key Type ASCII e PCH CR SELECT This will erase the Target device and you may recover by REPROGRAMing the TLM only 41 15 Introduction AVR Assembler AVR Assembler The AVR assembler in the IRTC will allow you to do most that a conventional assembler will and something s that it may not Itis a single pass interpreted assembler with conditional statements such as IF THEN IF ELSE THEN BEGIN UNTIL BEGIN WHILE REPEAT BEGIN AGAIN The syntax of the assembler is not that of Forth Reverse Polish or Postfix notation but standard Prefix This means that the source looks like standard assembly but with space delimiters e g LDI R26 0x01 becomes LDI TOSL 01 As with all assemblers this checks the validity of the addressing mode for the instruction and the size of the data This is accomplished by flags that are set to indicate the various addressing modes Note The only forward referencing available in the assembler is with the structures above and the skip instructions ofthe AVR Conditional Flags Register Use Macros The conditionals require a flag test CS O 0 lt 0 gt gt HS TS OV or IE before their use Each may be followed by a NOT to produce the inverse of th
45. n both cases BEGIN WHILE REPEAT Use BEGIN words flag WHILE words REPEAT This is perhaps the most powerful of the Forth control structures The loop starts at BEGIN and executes all the words as far as WHILE If the 16 bit flag on the data stack is true non zero the words between WHILE and REPEAT are executed and the cycle returns to BEGIN If the flag tested by WHILE is false zero the loop is terminated WHILE consumes the flag CASE OF ENDOF ENDCASE Use CASE S b valuel OF words ENDOF value2 OF words ENDOF default words otherwise clause ENDCASE The case statement used in IRTC is the result of a competition run by the Forth Interest Group FIG in the USA It was invented by Dr Charles E Eaker and was first published in Forth Dimensions Vol II No 3 CASE exists to replace large and unwieldy chains of IF ELSE THEN statements The function of CASE is to execute one action dependent on the 16 bit value passed to it on the stack The OF words compare valuel 2 etc to the stack value and if equal the words between OF and ENDOF are executed the structure is then exited If no match is found the Quick Forth Guide words between the last ENDOF and ENDCASE are executed with the input stack value still on the data stack FOR NEXT Use index FOR words NEXT This is the simplest counted loop in IRTC The index is transferred to the Return Stack and the words b
46. n the TLM there are many is the simplest and called a Round Robin tasker Basically each task is a separate program that is often self contained The tasks run until they reach a point where they have to wait for something at this point a task PAUSEs and the next runs If the task does not have a natural wait then a PAUSE must be added at some convenient point or the task STOPped These tasks are said to be co operative that is they must relinquish control of the processor to allow others to have a go Each task has it s own stack space and an area called USER Here resides the links to the tasks memory plus variables that may be used only by that task One example of these is BASE used by the numbers described elsewhere A task is given aname and the sizes of the Data stack Return stack and User area these are then allocated to it by TASK The stacks work down from their tops and the user area goes up as shown below The USER area starts with the address of the next task area to link to and is called STATUS The other bytes defined by IRTC are show below Name Location Function STATUS UP 0 The link to other tasks and the RESTing AWAKEN flag DPO UP 2 The address of the bottom of the Data stack HANDLER UP 4 The exception return address for CATCH and THROW VFLAG UP 6 The TO variable flag BASE UP 8 The radix for number conversion PTR UP 10 The pointer for number to ASCII conversion PAD UP 24 General ar
47. nd implements multitasking This small program is however self contained It requires no further code to allow full modification and inspection of all the AVRs resources This is all carried out by the word SERVER which is defined as follows SERVER S BEGIN ADDR EXECUTE A5 CHAR OUT AGAIN We must thank the University of Rostock Germany for this deceptively simple idea The words ADDR waits for the Host to send two bytes of data LSB first to the Target stack This 16 bit value must be a valid CFA Code Field Address of an existing Target definition The word EXECUTE performs a IJMP to this address The A5 CHAR OUT is used as an acknowledgement for the communications The basic TLM words are ADDR C C EXECUTE PAUSE SERVER SPO STOP WORD gt With only these it is possible for SERVER to interrogate the AVR internals For example if we wish to look at the current value of the SREG register we need to perform a C on file address 3F and send the result to the Host for display This is what happens I O SREG CQ H lt cr gt Host sends CFA of ADDRQ EXECUTE runs it Host sends 3F SREG adds which ADDR puts on Target stack Host sends CFA of C EXECUTE runs it and C fetches the value Host sends CFA of WORD gt EXECUTE runs it and sends result to Host Host displays the 8 bit value in Hex SPQ puts the value of the stack pointer DP on the stack so
48. of Forth and are the starting point from where the Forth grows or extends Hence the Forth language is termed extensible To recap Forth is an extensible language that consists of a dictionary of words each defined in terms of other words One of the many advantages of Forth is it s ability to execute a word from the dictionary by name Once a colon definition has been entered it may be run or executed just be typing the word name and pressing the RETURN key Forth is thus called an interactive language because it carries out your commands as soon as you enter them at the keyboard When the RETURN key is pressed Forth tries to run all the words on the command line and at the end prints ok 15 Quick Forth Guide The Stack This is true providing no problem was found For instance if a word is not in the dictionary Forth will say Error lt word gt is undefined Or one of the words may not have enough parameters and you may see stack underflow Forth is a stack based language This means that all the parameters used during operations or calculations are held on a stack The stack is a Last in First Out LIFO structure in the re writable area of computer memory If we put a value on the stack we say we are pushing it onto the stack If we retrieve it we say we are popping it off the stack This stack operation is very useful but leads to some differences Suppose we wish to add two numbers PRINT 1 2 3 This is
49. om the target system and requires the following connections to the target processor Pin1 Black GND 0 Volts Pin2 Red VCC 5 Volts Pin3 Blue MOSI Master Out Slave In Pin5 Green MISO Master In Slave Out Pin7 Black SCK Serial Clock Pin9 White RESET Target CPU Reset The ISP must also be connected to the host computers serial port COM1 4 It may be necessary to use a 25Way to 9Way convertor or cable to enable proper connection The Target and the ISP should be powered up together to ensure they reset properly It is also important that the ISP is connected to an operating serial port with PC running prior to power up Checking the fuses Signatures Commands 52 It is possible to get the Target CPU out of step with the ISP This may be caused by noise especially on the SCK line or bad earthing of the PC and power supplies In some cases the signature bytes may read as FF If this occures check the fuses with FUSES this should return 0F If not use SOF FUSE to correct REM should now return the proper signature bytes The AVR chips all have a 3 byte signature For example the 9088515 is 01 93 1E These are set in the value SIGNATURE in the INI file When you do a REM the Target chip signature is checked against the set value If they do not agree IRTC will not allow remote access In the case of the Megal03 the bytes should be 01 97 1E but in some devices they are 01 01 1E If you have s
50. ome of these you may correct for this by editing the Megal103 INI file A SET ADDRESS Sets the address to be programmed next C WRITE PROGH Write a code byte high c WRITE PROGL Write a code byte low D WRITE DATA Wite a byte to EEPROM at address set d READ DATA Read a byte from EEPROM e CHIP ERASE Erase the Code and Lock bits F READ F amp L Read the Fuses or Lock bits f WRITE FUSE Write the Fuses L DEV Put the programmer in the Development mode RS232 pass thru 1 WRITE LOCK Write the Lock bits Interactive Serial Programmer m WRITE PAGE Write a 256 byte page Megal03 603 only P PROG ENABLE Enable the program mode returns 53 if successful p PROG TYPE Returns S to show a serial programmer R READ PROG Reads the Code memory at the address set S IDENTIFIER Returns RAM ISP to show programmer s READ SIGNATURE Returns the signature byte at the address specified T GET DEVICE Sets the device code for AVR to be programmed V SOFT VER Returns the software version v HARD VER Returns the hardware version Z TRI STATE Tri states the programmer pins and sets reset high to run the Target GENERAL Sends the byte received out of SPI and returns the SPI byte clocked back 53 17 Object Save and Load Object Save and Load IRTC when in the Host mode will compile an application very quickly However when it has been written and debugged it may be desirable to save the
51. on 21 Further Information Forth Interest Group UK http www users zetnet co uk aborigine forth htm Forth Interest Group USA http www forth org fig html 63
52. opcode and that it does not corrupt the TLM file space or stack To test parts of your code it may be necessary to insert return opcodes into the code at strategic points and then create stubs to test that section Interrupts in the AVR are done via vectors in the first 48 bytes of the program memory space To enable these vectors to be changed during development the TLM has 96 locations programmed to jump indirectly to locations at the start of the development code RAM These RAM locations may then be programmed with an absolute jump address to the interrupt routine This adds about 3 5uSecs to the interrupt latency at 6 MHz The Forth word VECTOR takes a vector number 1 24 and the interrupt address to automatically create the jump in the RAM location To return from a RAM vectored interrupt you should use the VEC RETURN function that pops the N ZL ZH and SREG that were saved as part of the VECTOR execution Note This is only possible in the larger AVR devices with JMP instructions that allocate 4 bytes for the interrupt vectors from 0000 In the smaller devices it is necessary to change the interrupt vector and REPROGRAM The word INTERRUPT may be used to define an interrupt routine instead of CODE or LABEL The associated interrupt vector address must preceed INTERRUPT and it will create a JMP or RJMP to the routine in the code vectors This will only take effect when the whole image is REPROGRAMed The function VEC SAVE may be used
53. ost definition of CONSTANT and enter the compile state for the Target DOES gt starts by compiling into the Target a CALL DODOES The code following DOES gt will then be compiled into the Target dictionary The address where this compilation takes place is patched into the definition of CONSTANT in the Host So when we invoke CONSTANT in our program the address of the code compiled by DOES gt will be compiled into the Target followed by the value on the Host stack So when the resulting constant is run in the Target it runs CALL DODOES This leaves the address of the value that was on the Host stack at compile time on the Target stack The code compiled after DOES gt is then run This results in the fetching of the compiled value from the code space onto the Target stack The word CONSTANT will now create as many more words as we wish all with the same resultant run time action but each with 1t s own result Those who know of the Object Oriented Programming style OOPs may recognise this construct For more insight into this you may wish to refer to the Appendix Note The example shown here for a constant is not that used by TLM It is only a simple demonstration of the CREATE DOES gt structure end of guru warning Demo Application Loading the Demo 24 Now we have communication with the TLM we may see what can be achieved Try the following 12 er Error is undefined As this is the start we do not have many Fo
54. photocopied reproduced or translated to another language without the prior written consent of RAM Technology Systems and MicroProcessor Engineering The information contained in this document is subject to change without notice Distribution of application programs Binary code produced with this compiler and tools may be freely distributed without royalty No source code provided by MPE or RAM Technology may be distributed without written permission first being granted Warranties and support We try to make our products as reliable and bug free as we possibly can We support our products If you find a bug in this product and its associated programs we will do our best to fix it Please check first by fax or email to see if the problem has already been fixed Please send us enough information including source code on disc or by email to us so that we can replicate the problem and then fix it Please also let us know the serial number of your system and its version number We will then send you an update when we have fixed the problem The level of technical support that we can offer may depend on the Support Policy bought with the product Technical support will only be available on the current version of the product Make as many copies as you need for backup and security The issue discs or CD are not copy protected The code is copyrighted material and only ONE copy of it should be use at any one time Contact MPE or your vendor for det
55. rd being parsed If the word is not found the next vocabulary in the list will be searched and so on until the word is found or the list expires IRTCis set to remove the necessity for you to need to modify this order during normal operation Only is you wish to modify the compiler or do special operations to create new Library definitions will this order need to be changed You will notice that the Host and Remote modes have different vocabularies selected Below is a list of the functions and their vocabularies ROOT This is the root vocabulary and is always present It contains words that allow the search order to be changed and the other vocabularies to be selected FORTH This is the main vocabulary that contains the usual Forth words These are the Host definitions that run IRTC and relate to the PC processor METAAVR Here are the meta compiler functions that make up IRTC XASM The AVR assembler mnemonics registers and flags are in here This is only searched if a CODE or C C definition is being compiled TRANSITION Many of the words in here are replicas of those in FORTH These are the optimisers for IRTC and this vocabulary is the first to be searched during a Target definition LIBRARY These are the Library macros that compile the Target code and create the Target vocabulary entries TARGET The Target vocabulary contains the words that exist in the AVR code space These words may be interactively executed All Tar
56. rth words loaded yet To help with interactive development any word in the Library may be loaded from the keyboard with REQUIRED e g REQUIRED cr ok 12 er 3 ok Which shows that the TLM can add 1 and 2 to get 3 providing that the necessary resources have been supplied to it All seems to be working so let us jump up to the real thing and try a multi tasked program with timer driven interrupts Quick Forth Guide Type FLOAD LDEMO cr T Unresolved references No words Unresolved Statistics Last Host Address 4AE54 Last Target Code Address 4B2 Last Variable Address 2E3 Last EEPROM Address 0 ok T What happened First we input FLOAD LDEMO FLOAD is the Forth word for File Load It takes the next space delimited word in the input string as a file name and tries to interpret the contents It has the same effect as you typing the file contents at the keyboard These are ASCII text files You will notice that no file extension was used FLOAD assumes FTH if no extension is given So 1f you use FTH for all your files then you may refer to them by name only The file LDEMO FTH asks for other files to be loaded to make up the demo program As each one loads it s path and name appear at the top of the screen Running the Demo Now you have loaded the demo let s run it Type GO cr TTY EX ABCDEFGHIJ 123456789 ABCDEFGHIJ ABCDEFGHIJ 123456789 ABCDE
57. s allow you to alter this by a branch or loop The change is often brought about by a piece of runtime data This gives the program the ability to choose which direction it will take Control structures must be used inside a definition and may not start in one definition and finish in another They cannot be used directly from the command line But they may be nested inside one another as long as they do not overlap 19 Quick Forth Guide 20 IF THEN Use flag IF true words THEN The 16 bit flag controls the outcome and is consumed by IF If the flag is non zero the true words are executed otherwise they are not If the flag is required again it may be duplicated by DUP If the flag value is only required between IF THEN it may be conditionally duplicated by DUP IF ELSE THEN Use flag IF true words ELSE false words THEN This is similar to IF THEN above but with execution phrases for both true and false zero values of the flag BEGIN AGAIN Use BEGIN words AGAIN This structure forms an endless loop that is only terminated by a AVR reset This is often the structure used in your application run word BEGIN UNTIL Use BEGIN words flag UNTIL This structure forms a loop that is always executed at least once The loop will return to BEGIN as long as the 16 bit flag is false zero when tested by UNTIL As soon as flag is true non zero the loop is terminated The flag is consumed by UNTIL i
58. t STREAM gt Each task acquires the pipe in turn to place it s ASCII string As the pipe is shorter than the strings the semaphore is necessary to stop the strings getting intertwined Only when STREAM is zero may a task ACQUIRE the pipe From then on only that task may use the resource 11 Pipes An extension to TO variables has been added to the TLM These are byte pipes or byte oriented First In First Out FIFO structures These are particularly useful when using tasks refer to the demo These pipes may be up to 256 bytes long and are used as TO variables Values sent TO the pipe are placed in the next available byte If the pipe is full the task is PAUSEd until the pipe is free If a task tries to take a byte from an empty pipe the task is PAUSEd until there is a byte to take If a pipe only links two tasks there is no need for a semaphore Only if more that one task takes or puts data into a pipe is the semaphore required To define a pipe use 10 BYTE PIPE lt name gt lt cr gt Before a pipe may be used it must be initialised The size of the pipe and it s address in the variable space are saved when it is defined To initialise it the address of the definition is required A or ifin a colon definition will provide the address for INIT PIPE lt name gt INIT PIPE lt cr gt or within a colon definition lt name gt INIT PIPE 35 12 Host Programs Host Programs It is possible to
59. t is the beginning of the Target development code space The Variable space is set by VORG Use 0060 VORG Tests on the validity of the memory spaces are done at compile time The following VALUEs may be altered to reflect your memory by editing AVR xxxx INI ROM START set to 0000 ROM END set to FFFF RAM START set to 0060 RAM END set to 03FF 27 Meta Compiling and the TLM 8 Meta Compiling and the TLM Meta Compiling Meta Compiling as its name implies is the creation of something from itself IRTC generates a Forth for the Remote Target from the host Forth running on the PC Meta Compiling is often also called Cross Compiling as the host and target CPUs are different When in the Host mode we Meta compile and create a Target image inside the PC This image cannot be executed here as the code is for the AVR processor However the resultant code may be transferred Downloaded to the Target or to an programmer In both cases the result is code generation that may be run in the Target When in the Remote mode we compile and create a Target image in the Host and in the Target This is slower as we have two things to do and one is via a serial link But the result is instant code that may be executed Which approach is used depends on the position you are in with your application To begin with you would experiment in the Remote mode until a section of code was written and debugged Later you may compile and download the kno
60. tem In IDE gt MacroManagement set the ACROBAT macro to the full path name of the PDF file viewer normally Adobe Acrobat for example C APPS ACROBAT ACRORD32 EXE Edit the macros in the file XAVR DEMO DEMO CTL to reflect the directories you are actually using Test that the system is working by clicking on the AVR icon on the top left toolbar The ISP is connected to your IBM compatible computers serial port COM1 to COM4 IRTC sets the port configuration to 38400 baud 8 bits one stop bit and no parity The ISP 25 way D type connector is then plugged into your computer port or via a cable If the ISP is not connected to COM1 edit the KERNEL INI files to use SET COMx where xis 1 4 The header on the 10 way strip cable is plugged into a pin header on your Target hardware The Target powers the ISP through the strip cable via the power pins from your Target See the ISP description Now read the rest of the manual or go to the DEMO chapter Installation and Configuration Overview 3 Overview The philosophy behind IRTC is that of a high level interactive de bugger Through TLM the AVR is made into a stack machine with three functions e Data may be transferred from the Host PC to the TLM stack e Data may be transferred from the TLM stack to the Host PC e The TLM may execute code at an address placed on its stack These three functions are all that is required to test individual Forth words or ass
61. ters AVR Reg name AVR Reg number s Forth use Other Function Z ZH ZL R31 30 Scratch Used for IJMP Y YH YL R29 28 Data Stack Pointer X XH XL R27 26 TOS top of data stack Memory and AVR Registers R25 24 SEC intermediate R23 22 UP user pointer R21 20 N 5 N 4 scratch R19 18 N 3 N 2 scratch R17 16 N 1 N scratch 10 Target Configuration files Target Configuration files The way the Target AVR is used is defined bye the file xxxx INT This is loaded by IRTC and extends XAVR EXE by compiling the AVR set up words and the talker TLM code The positions and size of the memory spaces and stack positions are set Below is the source for MEGA103 INT Initialisation File for MegaAVR 38400 8 NOPARITY ONESTOPBIT SET COM1 META IN META SET FE IN META 0060 VALUE RAM VEC 00A0 VALUE RAM STAR SOFFF VALUE RAM END 0000 VALUE ROM STAR7 SFFFF VALUE ROM END 0000 VALUE EPROM START SOFFF VALUE EPROM END Vectors 0000 CONSTANT RESET 0002 CONSTANT EXT INTO 0004 CONSTANT EXT INT1 0006 CONSTANT EXT INT2 0008 CONSTANT EXT INT3 SOOOA CONSTANT EXT INT4
62. to push N ZL ZH and SREG registers so that the VEC RETURN may pop correctly TIMO OVF INTERRUPT lt name gt VEC SAVE interrupt code JMP VEC RETURN C Or END INTERRUPT During development the above interrupt would be coded as CODE lt name gt X TIMO OVF INTERRUPT lt name gt Dumps X VEC SAVE interrupt code JMP VEC RETURN C SET TIMO OVF INT XASM 17 lt name gt VECTOR T The SET TIMO OVF INT is run during the initialisation to set the RAM vector The interrupt may then be tested and when operational the CODE lt name gt replaced by the LIT ERAL or LIT END INTERRUPT ERAL AVR Assembler TIMO OVF INTERRUPT lt name gt and VEC SAVE If your interrupt code may be coded with only the use of the N ZL ZH and SREG registers you do not need to save any other resourses To assist with code definitions in particular memory dump utilities DUMP RDUMP IDUMP FDUMP and EEDUMP are available DUMP FDUMP and EEDUMP require a start address and the number of bytes to dump DUMP is for the code memory e g 0000 50 DUMP Register File Dump The register file space may also be dumped by using REG DUMP This shows the contents of all the file registers from RO to R31 1 O File Dump The I O file space may also be dumped by using IO DUMP This shows the contents of all the I O
63. wn code and then continue in the Remote mode to debug more What happens when we Meta Compile is quite simple deceptively so IRTC parses the ASCII text from a file or the keyboard and interprets the result That is every space delimited word is searched for in the vocabularies shown in the right corner of the screen If found the word is executed in the Host PC What happens as a result depends on the mode Host or Remote and on a variable STATE T If we are in Host and STATE T is false the word if found will execute in the Host PC leaving its result on the Host stack if necessary Any Target words will not be found in this state so will result in the message Error word is undefined If we are in Remote and STATE T is false the word will execute in the Host PC and if a Target definition its Code Field Address CFA will be sent to the Remote Target for execution there also Any stack result will be left on the Remote Target stack If we are in Remote and STATE T is true the word executes in the Host PC and if a Target definition its CFA is sent to the ISP to be placed in the next Target dictionary location This is the Remote compile mode set by encountering a or As can be seen the Host executes everything it finds in the Target vocabulary If STATE T 1s false the Remote Target executes the resulting CFA if not it compiles it for execution later when the new definition is run Any definition found by IRTC that is not
64. y be reassuring to see the result At the moment there is no de compiler in IRTC However it is possible to create a HEX file of your code with O HERE T HEX SAVE TEST We may view the code by using the Atmel Studio debugger and step through the code with it Controlling a Port Now we have communication we may modify any of the RAM locations hence the ports The command FDUMP will list all the file locations and C will return the value of a single location 21 Quick Forth Guide Comments To read from PortA all we need is I O PORTA C H This returns the value of PortA all the registers and flags are known to IRTC if you use one from a device other than the one chosen an error will be issued To write to PortA first DDRA must be set to an output on the port pin we wish to use Say we are using bit 0 then we could set this to an output with 01 1 0 DDRA C The port bit may then be set high with 1 I O PORTA C or low with 0 I O PORTA C The same applies to any other port timer or internal function Comments may be incorporated into your source in three ways COMMENT COMMENT or Y to end of line or S COMMENT to COMMENT is used to enclose several lines of comment The ignores any further text on that line only Starting a block of lines with may be used instead of COMMENT The or S ignore all text until the is encountered This is used for the stack

MPE IRTC Forth for the ATMEL AVR series

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