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Allen-Bradley OS-9 Assembler-Linker

1. built in functions for calling OS 9 and generating system trap calls Supports use of position independent re entrant code allows programs to be written and assembled separately and then linked together which allows creation of standard subroutine libraries full macro capabilities can generate stand alone 68000 68020 code This manual describes how to use the Macro Assembler package and also discusses very basic programming techniques for the OS 9 environment It is not intended to be a comprehensive course on 68000 assembly language programming If you are not familiar with these topics you should consult the Motorola 68000 programming manuals and one of the many assembly language programming books available at bookstores and libraries Preface Installation Concering This Manual The distribution disk or tape contains a number of files that should be copied to the working system disk according to the accompanying instructions The original distribution media should then be stored in a safe place for backup purposes The executable files for r68 and 168 should be copied to the system s execution directory OS9 68000 systems are generally supplied with these files already present in the CMDS directory The DEFS and LIB directories contain include files that resolve system definitions On OS 9 68000 systems the DEFS and LIB directories should be located on the root directory of the system default working disk d
2. In the following three instructions the shift direction d may be 1 for left or r for right Mnemonic Description Isd s Dx Dy Logical shift data Isd s lt data gt Dy Logical shift immediate Isd ea Logical shift memory move s ea ea Move from source to destination move ccr ea Move from condition codes This instruction is not available on the 68000 The 05 9 Kernel will emulate this instruction on the 68000 to allow user state code to be easily transported from 68000 to 68010 68020 move ea ccr ove to condition codes move ea sr ove to status register move sr ea ove from status register This is privileged on the 68010 68020 Avoid this instruction in programs that are to execute in user state move usp An ove from user stack pointer move An usp ove to user stack pointer movea s lt ea gt An ove address w or l movem s ea reg list ove multiple Examples d0 d0 only d0 d4 a5 d0 d4 a5 d0 d7 a0 a5 dO through d7 a0 through a5 movep s dx d Ay Move peripheral data w or l from register to memory movep s d Ay dx Move peripheral data w or l from memory to register moveq I lt data gt dn Move quick Chapter 1 Basic Information About Assembler For the next instructions the following are valid registers for Rc SFC DFC CACR USP VBR CAAR MSP and ISP movec Rc Rn Move from control register
3. Location Flag 2 bytes Reference Offset 4 bytes The Reference Count indicates the number of References to follow Each Reference has both a Location Flag and Reference Offset The location is determined by bit 1 of the first byte and bit 3 7 of the second byte of the Location Flag unused settoQ gt Location Flag Byte 1 Location Flag Byte 2 Chapter 3 Relocatable Program Sections The value of Bit 1 in the first byte determines the interpretation of bit 5 in the second byte Byte 1 bit 1 Byte 2 bit 5 0 not remote 0 data 1 code 1 remote unused set to 0 The other location bits of the second byte are interpreted as follows Bits 3 4 Size of Reference to External Symbol 01 1 byte 10 2 bytes 11 4 bytes Bit 6 Relative Reference Flag If set this tells the linker that the reference is relative to the location of the reference Bit 7 Negative Reference Flag If set this tells the linker to add the negative of the symbols location when resolved The Reference Offset is the offset into the code or initialized data section where the Reference appears Local Reference Section Local References Count 2 Bytes The count indicates the number of local references that follow Local References Variable These are references in the code or initialized data areas that reference code or data in the psec
4. Tells the linker how much remote initialized data is contained in the module The size is determined by the total size of all the dc directives in the remote vsects Size of the Debug 4 Bytes This is determined from the size of assembled debugger code Name of Module Variable Length Null terminated ASCII string taken directly from the psect directive The linker uses the name to identify the psect in case of an unresolved reference or other error External Definition Section External Definition Count 2 Bytes The count indicates the number of external definitions that will follow 3 9 Chapter 3 Relocatable Program Sections The external definitions are placed in the linker s symbol table and can be referenced by any other module External Definitions Variable Each external definition has the following format Name 1 n bytes Type Definition 2 bytes Symbol value 4 bytes The type is determined by bit 0 of the first byte and bit 0 2 of the second byte unused setto0 9 S pope Type Part 1 d SRN Type Part 1 Type Part 2 The value of bit O of the first byte determines the interpretation of bit 0 2 of the second byte 0 not common 1 common Type Part 2 bit 0 bit 1 bit 2 0 data 0 not remote 0 uninitialized 1 initialized 1 remote 0 uninitialized 1 initialized 1 code or equ 0 code set to 0 1 equ unused set to 0 0 no
5. These are generally set and equ and possibly the lo and do statements These declare symbolic constants and symbolic offsets Labels on these statements are local to the assembly of the source file and are not usable during assembly of other program segments Additionally these statements cannot reference any global symbols For example the oskdefs file is intended to be included outside the psect of each source program Although technically a vsect can similarly appear outside the psect the usefulness of such a vsect is limited to defining the expected type of an external symbol as a data area symbol because no actual storage would be assigned to it by the linker 3 3 Chapter 3 Relocatable Program Sections Location Counters Diagram of Typical Program Layout nam example ttl sections and declarations labconstequ 1 Local constant definitions space equ 20 mode set 1 use h0 defs oskdefs Include local definitions file psect nam typ rev ed stack gblcode Start of psect vsect Start of nested vsect gblunin ds l 1 Global uninitialized data gblinit dc b string 0 Global initialized data locunin ds l 1 Local uninitialized data locinit dc b hello 0 Local initialized data ends End of vsect gblcode Global code label move l gblunin a6 d0 Global uninitialized data reference Global initialized data reference Internal code reference External code reference External data reference lea gblinit a6 a0 bsr s intcode
6. Unpack BCD 1 19 Chapter 1 Basic Information About Assembler 68881 Floating Point Coprocessor Mnemonics The 68020 assembler 168020 recognizes instructions and addressing modes referencing the 68881 floating point coprocessor This section applies only to the 68020 The following register names are reserved for referencing the 68881 and cannot be redefined or used out of context Register name Definition FPn Floating point register 0 7 FPcr Floating point control register FPsr Floating point status register FPiar Floating point instruction address register The assembler recognizes the following floating operand data format extensions Extension Description gc c 71 Byte Integer Word Integer Longword Integer Single Precision Real Double Precision Real Extended Precision Real x ojj TT s a The P packed decimal real data format is not supported Floating point constants can be given when a floating point instruction indicates immediate addressing Floating point constants can be given in decimal format or left justified hexadecimal format The size of the immediate data value is determined from the data format extension given on the floating point instruction Single precision values are stored internally as double precision and converted to single precision before storing into the instruction Extended precision constants can be given only as hexadecimal values Flo
7. dc w F900 S FA00 SFBO00 SFCOO dc b most programmers are strange people dc b 0123456789 ds Chapter 5 Pseudo Instructions Define Storage Syntax label ds s lt expr gt Function ds is used within vsects to declare storage for uninitialized variables in the data area s is a size specifier It may be b byte w word or 1 long lt expr gt specifies the size of the variable in bytes words or longwords depending on the size given for the ds extension This value is added to the appropriate uninitialized data location counter in order to update it When ds is used to declare variables a label is usually specified which is assigned the relative address of the variable In OS 9 the address is not absolute so indexed addressing modes are used to access variables The actual relative address is not actually assigned until the linker processes the ROF The remote data area must be accessed using the indexed register indirect with offset addressing mode n An Xn 1 Important ds w and as 1 align to an even byte boundary if the respective location counter is non even 5 5 Chapter 5 Pseudo Instructions dz 5 6 Reserve Zero Bytes Syntax label dz s expression The size extension s can be b for bytes W for words default for longwords Function dz is used to fill memory with a sequence of bytes each having a value of zero The 16 bit expression is used as the numb
8. For non mainline segments this word is informational only Size of Static Storage 4 Bytes Tells the linker how much static data storage to reserve for the module Chapter 3 Relocatable Program Sections This value is determined from the total size of the ds directives in the vsects Size of Initialized Data 4 Bytes Tells the linker how much initialized data is contained in the module The size is determined by the total size of all the dc directives in the vsects Size of the Object Code 4 Bytes This is determined from the size of assembled code Size of Stack Required 4 Bytes Tells the linker how much stack space the module requires The value is obtained directly from the psect directive Offset to Entry Point 4 Bytes Offset to the entry point in the object code The offset is relative to the beginning of the module The value is obtained directly from the psect directive Offset to Uninitialized Trap Entry Point 4 Bytes Offset to the entry point in the object code which is called when a tcall is made without installing the appropriate trap handler The offset is relative to the beginning of the module and is obtained directly from the psect directive Size of Remote Static Storage 4 Bytes Tells the linker how much remote static data storage to reserve for the module This value is determined from the total size of the remote ds directives in the remote vsects Size of Remote Initialized Data 4 Bytes
9. bsr extcode move l d0 extdat a6 rts vsect Start of nested vsect indat ds l 1 Local uninitialized data ends End of vsect intcode rts Local code label ends End of psect r68 maintains a set of address counters that keep track of relative memory addresses of object code initialized data uninitialized data and remote data It is important to remember that location counter values are relative and not the actual physical memory addresses Actual memory locations are not known until the program has been linked and loaded into memory The psect statement resets the instruction and data location counters and assembles subsequent instructions into the ROF object code file As object code is generated the instruction location counter is advanced accordingly An asterisk symbol can be used in expressions to refer to the current relative value of this counter Chapter 3 Relocatable Program Sections The vsect statement causes r68 to use the variable data location counters and places information about subsequently declared variables into the appropriate ROF data description area As variables are declared the initialized data location counter and the uninitialized data location counter are advanced accordingly An asterisk represents the value of the initialized data location The uninitialized data counter is not directly accessible You cannot preset any of the counters to a specific value there is no ORG statement for
10. cmp2 s lt ea gt Rn Compare register against bounds b w or Chapter 1 Basic Information About Assembler cc in the following instruction represents the branch condition code Mnemonic dbcc dn lt label gt Description Test condition decrement and branch divs ea Dn Signed divide divu lt ea gt Dn Unsigned divide divs w lt ea gt Dn Signed Divide 32 16 16r 16q divs ea Dq Signed Divide 32 32 32q divs lt ea gt Dr Dq Signed Divide 64 32 32r 32q divsl lt ea gt Dr Dq Signed Divide 32 32 32r 32q divu w lt ea gt Dn Unsigned Divide 32 16 16r 16q divu lt ea gt Dq Unsigned Divide 32 32 32q divu lt ea gt Dr Dq Unsigned Divide 64 32 32r 32q divul lt ea gt Dr Dq Unsigned Divide 32 32 32r 32q eor s Dn lt ea gt Exclusive OR eori s lt data gt lt ea gt Exclusive OR immediate eori lt date gt ccr Exclusive OR condition code eori lt data gt sr Exclusive OR status register exg Rx Ry Exchange registers extb I Dn Extend byte to longword exts Dn Sign extend w or jmp ea J ump jsr ea J ump to subroutine lea lt ea gt An Load effective address link An lt displacement gt Link and allocate link An lt displacement gt Link and allocate long displacement Chapter 1 Basic Information About Assembler
11. movec Rn Rc Move to control register Mnemonic Description moves s Rn lt ea gt Move to address space moves s ea Rn Move from address space muls ea Dn Signed multiply mulu lt ea gt Dn Unsigned multiply muls w lt ea gt Dn Signed Multiply 16 x 16 32 muls lt ea gt DI Signed Multiply 32 x 3232 muls lt ea gt Dh DI Signed Multiply 32 x 32 64 mulu w lt ea gt Dn Unsigned Multiply 16 x 16 32 mulu ea Dl Unsigned Multiply 32 x 3232 mulu lt ea gt Dh D Unsigned Multiply 32 x 32 64 nbcd lt ea gt egate decimal with extend neg s lt ea gt egate neg s ea egate with extend nop 0 operation nots ea Logical complement ors ea Dn nclusive OR register or d Dn lt ea gt nclusive OR memory ori s data ea nclusive OR immediate ori lt data gt ccr nclusive OR condition codes ori lt data gt sr nclusive OR status register pack Ax Ay adjust Pack BCD pack Dx Dy adjust Pack BCD pea ea Push effective address reset Reset external devices Chapter 1 Basic Information About Assembler In the following 6 instructions the shift direction d may be 1 for left or r for right Mnemonic Description rod s Dx Dy Rotate without extend register rod s lt data gt dy Rotate without extend immediat
12. Block Syntax label com s size The size extension s can be b for bytes W for words default for longwords Function com reserves an area of memory in the appropriate vsect for use as an overlaid common block The com label can appear in any number of psects The size of the data area actually assigned by the linker is the maximum of the sizes given on all the com statements for that label To facilitate initialization of common blocks the label is allowed to appear on initialized data directives In this case the data definition is used instead of the size given on the com statement The com statement can be used in a remote vsect to allocate a common block in the remote memory area Examples The following allocates a non remote data common block of 100 bytes Both references to block1 a6 in each file refer to the same address File t1 a vsect block1 com 100 ends clr b blockl a6 File t2 a vsect block1 com 100 ends clr b blockl a Chapter 5 Pseudo Instructions The following example demonstrates how initialization of a common block is done The first block2 com directive reserves 12 bytes of memory The block2 definition in s2 a defines initialized data for the common area The initializing data definitions supersedes the sizes given on any com directive Therefore for best results the sizes of the com directives and the amount of initializing data should agree File s1 a vsect bl
13. The operand field follows the instruction field They must be separated by at least one space or tab Some instructions do not use an operand field Other instructions and assembler directives require one to specify an addressing mode operand address and or parameters Some require a source operand and a destination operand Important See the specific instruction and assembler directive descriptions for the operand format if any Comment Field The last field of the source statement is the optional comment field It can be used to include a descriptive comment in the source statement This field is not processed other than being copied to the program listing Assembly Listing Format If the l option is given in the r68 command line a formatted assembly listing is written to the standard output path The output listing has the following format 00e6 64d2 bcc s label10 00ea b27c label cmp w ESEOF d1 copy result Comment field Start of Operand Field Start of Instruction Field Start of Label Field A symbol here indicates a macro expansion Start of Object Code Bytes An here indicates operand has an external reference Location Counter Value Evaluation of Expressions Chapter 1 Basic Information About Assembler Operands of many instructions and assembler directives can include numeric expressions in one or more places The assembler can evaluate expressions of almost any complexity using a form simila
14. Uninitialized Trap entry point offset This is used for handling user mode trap instruction processing Only give this parameter if the program includes code to handle uninitialized traps Otherwise omit this parameter do not use zero This parameter is used only in mainline psects Syntax vsect remote Legal Internal Statements ds de dz endsect align Relocatable Object File Format Chapter 3 Relocatable Program Sections The vsect is the variable storage section containing either initialized uninitialized variable or remotely addressable variable storage definitions Thevsect directive causes r68 to change the location counter from the code location counter to the data location counters The data location counter employed depends on the statement used and the presence of the word remote after the vsect directive There are four data location counters One for each of the following types of data initialized uninitialized remote initialized and remote uninitialized The initialized and uninitialized data are intended to be accessed by the 68000 register indirect with offset addressing mode n An Because the range of this addressing mode is limited to 64K the total size of these data areas is also limited to 64K The remote data areas are intended to be addressed with the 68000 indexed register indirect with offset addressing mode n An Xn l or the 68020 32 bit offset addressing modes These data areas ar
15. at all If a parameter list is provided the parameter list will be stored in the ROF for later use by the linker to generate the memory module header If no parameter list is provided the psect name defaults to program and all other parameters have default values of zero The elements of the psect parameter list are as follows Parmeter Definition name Up to 20 bytes for a name the linker uses to identify the psect Any printable character may be used except a space or comma however the name must begin with a non numeric character The name does not need to be unique from other psect names but itis easier to identify psects that the linker has problems with if the names are different typelang A word expression used as the executable module type language word If the psect is nota mainline segment the type language word must be zero attrev A word expression used as the executable module attribute revision word edition A word expression used as the executable module edition word stacksize A long word expression that estimates the amount of stack storage required by pthis psect The linker totals the value in all psects to appear in the executable module and adds the value to any stack storage requirement for the entire program entrypt A long word expression used as the program entry point offset for psect goes here If the psect is not a mainline segment this is 0 trapent A long word expression indicating the
16. blank lines in the listing The value of the operand determines the number of blank lines to generate which can be an expression constant or name If no operand is used a single blank line is generated rept endr Chapter 4 Assembler Directive Statements Repeat Assembly Sequence Syntax rept lt expr gt lt statements gt endr Function rept repeats the assembly of a sequence of instructions a specified number of times The result of the operand expression is used as the repeat count The expression cannot include external or undefined symbols rept loops cannot be nested Example 20 cycle delay REPT 10 4 9 Chapter 4 Assembler Directive Statements use Use External File Syntax use pathlist use pathlist use lt pathlist gt Function use statements cause the assembler to temporarily stop reading the current input file It then requests OS 9 to open the specified pathlist from which input lines are read until an end of file occurs At that point the latest file is closed and the assembler resumes reading the previous file from the statement following the use statement use statements can be nested for example a file being read due to a use statement can also perform use statements up to the number of simultaneously open files the operating system allows usually 29 not including the standard I O paths Full or relative pathlists may be specified If a relative pathlis
17. file created and maintained by r68 This file has a 1K buffer to minimize disk accesses Therefore programs that use more than 1K of macro storage space should be arranged so that short frequently used macros are defined first so they are kept in the memory buffer instead of disk space Macro Arguments Chapter 2 Macros The body of a macro definition may contain a call to another macro The definition of a new macro within another however is not permitted Macro calls may be nested up to eight levels For example the following macro consists of two iterations of the mac1 macro times2 macro macl macl endm Arguments permit variations in the expansion of a macro For example you can use arguments to specify operands register names constants or variables in each occurrence of a macro A macro can have up to nine formal arguments in the operand fields Each argument consists of a backslash character and the sequence number of the formal argument M V2 9 When the macro is expanded each formal argument is replaced by the corresponding text string actual argument given in the macro call You can use arguments in any part of the operand field not in the instruction or label fields Formal arguments can be used in any order and any number of times For example the macro below performs the typical instruction sequence to an I WritLn writ macro moveq 1 d0 Get path moveq 2 dl1 Number of chars to write lea N3 a
18. in this section can reference global symbols properly defined in other program segments Statements in this section may also appear in linkage maps and symbolic debugger symbol lists The psect is terminated by a matching ends or endsect statement Global and local variable storage are declared inside one or more vsects within the psect Vsects are usually nested within a psect but vsects cannot be nested within themselves A variable declaration section begins with a vsect statement and ends with an ends or endsect statement There are two types of variable declarations initialized and uninitialized These correspond to the assembly language storage allocation mnemonics dc and ds respectively 168 combines all initialized variable declarations from all program segments into a single initialized data memory area Similarly all the uninitialized data declarations are combined into a single uninitialized data memory area There is a third type of vsect declaration regarding remote data This vsect accumulates large amounts greater than 32K of data declarations The linker places remote vsect declarations after the end of the initialized and uninitialized data allocation The size of the remote data area is limited only by the amount of physical memory on the system Important Instructions accessing the remote data area must use long 32 bit indexed addressing modes Certain types of statements can appear outside usually before the psect
19. symbols Scans library for forward reference conflicts 0 Displays the local relocation information r Displays the external references r Displays the external references The Assembly Language Writing and testing assembly language programs using r68 and 168 Program Development involves a basic edit assemble link and test cycle The assembler and Process linker can simplify this process if programs are written in sections that can be assembled separately then linked together to form the entire program If one program section must be changed for any reason then only the revised section has to be reassembled The following is a summary of the steps involved in the assembly language development process 1 Create a source program file using the text editor 2 Run the assembler r68 to translate the source file s to a relocatable object module s 3 If necessary use the text editor to correct any errors reported by r68 in the offending source file and repeat step 2 4 Combine all required relocatable modules using the linker 168 If the linker reports errors correct them and repeat step 2 5 Run and test the program The OS 9 system state debugger or user debugger debug is frequently used to test programs 6 If bugs are found in the program use the text editor to correct the source file and then repeat the above steps Running r68 Chapter 1 Basic Information About Assembler r68 is a command progr
20. the module Consequently if a relocatable symbol is used in one of these expressions it must be subtracted from another relocatable symbol so that the result is a constant Expression Operators Operators used in expressions operate on one operand negative and NOT or on two operands all others The following table shows the available operators listed in the order they are evaluated relative to each other that is logical OR operations are performed before multiplications Operators listed on the same line have identical precedence and are processed from left to right when they occur in the same expression Assembler Operators By Order of Evaluation Character Description Character Description negative e logical NOT amp logical AND logical OR T multiplication division addition subtraction lt lt shift left gt gt shift right Chapter 1 Basic Information About Assembler 1 10 Logical operations are performed bitwise that is the logical function is performed bit by bit on each bit of the operands Division and multiplication functions assume unsigned operands but subtraction and addition functions work on signed 2 s complement or unsigned numbers Division by zero or multiplication resulting in a product larger than 4294967295 have undefined results and are reported as errors Expressions Involving External Symbols An external symbol is a symbol whose value is not known a
21. 0 Assembly Language Mnemonics 0 00s eee eee 68881 Floating Point Coprocessor Mnemonics Ls Floating Point Condition Predicates used for CC ssuuu Constant ROM Table sessleeeeeee ee Macros Chapter 2 Introduction to Macros eesseeeeeee ee Macro Structure 0 0 eee tenn eens Macro Arguments 0 0 ccc eect eee ne nee Macro Automatic Internal Labels 0 000 0000 e eee eee Relocatable Program Chapter 3 Sections Relocatable Program Sections 0 0 0 c eee eee eee eee Program Section Declarations Psect and Vsect 04 Location Counters ois iain eee be oH SRG BEER RA eA The Mainline Segment 0 0 cee eee eee The Psect Directive 0 0 ccc The V sect Directive ses cese eL whe Medion whee Ue e ed Relocatable Object File Format 0 0 0 0 cee eee ee eee Assembler Directive Chapter 4 Statements What Are Directive Statements n n nananana 000 ce eee eee eee end te hits Mand Hebets debe pee ids es da ds e See RES QUI SEU i t cae Dad nae De oath ee aa need ed Genes ee fail oiocdudtn agradne m acr Geter eee e e eens If else setides us eset jhe eg webs Ree Neds E CURE CERES wd DEL EP Hoa Soe cobs Med bee eS he ee SS Rees ee ee prr PME r pt endr i ioldse aed AG RARE ARE a edere re derriere s pc cape Mea wate adowass sete wea nkes dee ede deeb 5 Table of Contents Pseudo
22. 000000 00000001 00000002 00000000 0000 41 0001 5a 00000002 000025379 0012 4675 0043 4 70 004c 2020 00000071 Edition Typ Lang Attr Rev StdIn StdOut StdErr Char LowBound HiBound HelpStr HelpLen or from lower case to upper case with u option use defsfile equ 1 equ Prgrm lt lt 8 Objct equ ReEnt lt lt 8 0 psect updn Typ_Lang Attr_Rev Edition 1024 UpDn equ 0 standard input path equ 1 standard output path equ 2 standard error path vsect ds b 1 one character I O buffer dc b AR low bound to convert de b Zt upper bound to convert ends dc b Syntax updn u CSLF dsp Function converts upper to lower C LF dc b Options CSLF deb u converts lower to upper CSLF CSCR equ HelpStr Entry Point and Initialization 0078 600e 007a 101d 007c b03c 0080 671e 0082 b03c 0086 6606 PrsOpt bra s PrsOpt10 parse options move b a5 d0 get parameter byte cmp b d0 parameter leadin beq s PrsOpt20 branch if so cmp b CSCR dO carriage return bne s PrtHelp abort if not Appendix A Example P rogram A 2 0088 51cd 008c 602a 008e 7002 0090 41fa 0094 223c 009a 4e40 009e 604c 00a0 5345 00a2 65ea 00a4 101d 00a6 0a00 00aa 0200 00ae 66de 0050 3d7c 0056 60d0 0008 7000 00ba 7201 00bc 41ee 00c0 4e40 00c4 6520 00c6 102e 00ca b02e 00ce 650c 00d0 b02e 00d4 6206 00d6 0a2e 00dc 7001 00de 7201 00e0 4e40 00e4 64d2 00
23. 5X1 Telex 43 11 016 Hong Kong Canada FAX 414 382 2400 Tel 852 887 4788 Tel 519 623 1810 Telex 780 64347 FAX 519 623 8930 FAX 852 510 9436 PN 955113 19 Printed in USA
24. 6 a0 Get address of buffer os9 ISWritLn endm This macro uses three arguments VM for the path number WV for the number of characters to write 3 for the address of the buffer When writ is referenced each argument is replaced by the corresponding string given in the macro call for example writ 1 2 Buf The macro call above is expanded to the code sequence moveq 1 d0 moveq 2 d1 lea Buf a6 a0 os9 IS Writln Chapter 2 Macros Macro Automatic Internal Labels If an argument string includes special characters such as backslashes or commas the string must be enclosed in double quotes An argument may be declared null by omitting all or some arguments in the macro call This makes the corresponding argument an empty string so no substitution occurs when it is referenced There are two special argument operators that are useful in constructing more complex macros They are Operator Description Ln Returns the length of the actual argument n in bytes Returns the number of actual arguments passed in the given macro call These special operators are most commonly used with r68 s conditional assembly facilities to test the validity of arguments used in a macro call or to change the way a macro works according to the actual arguments used When macros are performing error checking they can report errors using the fail directive For example you could expand the writ macro on the previou
25. ALLEN BRADLEY Wy OS 9 Assembler Linker User Manual Copyright and Revision History Disclaimer Reproduction Notice Trademarks Copyright 1991 Microware Systems Corporation All Rights Reserved Reproduction of this document in part or whole by any means electrical mechanical magnetic optical chemical manual or otherwise is prohibited without written permission from Microware Systems Corporation Portions of this manual were previously published under the title OS 9 68000 Macro Assembler User Manual This manual reflectsedition 67 of r68 edition 95 of r68020 edition 64 of 168 and edition 47 of debug These versions are to be used with Version 2 3 or greater of the OS 9 Operating System Publication Editor Walden Miller Eileen Beck Revision H Publication date March 1991 Product Number ALD 68NA 68 MO The information contained herein is believed to be accurate as of the date of publication However Microware will not be liable for any damages including indirect or consequential from use of the OS 9 operating system Microware provided software or reliance on the accuracy of this documentation The information contained herein is subject to change without notice The software described in this document is intended to be used on a single computer system Microware expressly prohibits any reproduction of the software on tape disk or any other medium except for backup purposes Distribution of this
26. Bad operator Bad option Bracket missing Can t open file Appendix Assembler and Linker Error Messages When r68 detects an error it prints an error message in the listing just before the source line containing the error It is possible for a statement to have two or more errors in which case each error is reported on a different line preceding the erroneous source line If the assembler listing is inhibited by the absence of the 1 option error messages and printing of erroneous lines still occurs At the end of the assembly the total number of errors and warnings are given as part of the assembly summary statistics The error messages erroneous source lines and the assembly summary are all written to the assembler task s error status path which may be redirected by the shell For example r68 sourcefil o sourcefile o src error Note that calling the assembler with the listing and object code generation both disabled by the absence of the 1 o options can be used to perform a quick assembly just to check for errors This allows many errors to be found and corrected before printing of a lengthy listing For example r68 sourcefile Sometimes the assembler will stop processing of an erroneous line so additional errors following on the same line may not be detected so corrections should be made carefully Error messages consist of brief phrases which describe the kind of error the assembler detected Each error message is
27. Instructions Chapter 5 OS ECCE The Linker Chapter 6 Understanding the Linker 0 0 0 eee eee eee ee eee The Root Psect acc ca ati hos iei MER BE a AA Re RETE RE Subroutine Pset i eru ap eae a ia eke ER YU hee Hee ERA E The Linker Execution 00 00 cece cece e Linker Library Files Linker Defined and Linker Recognized Symbols The Linker Command Line 0 000 cece eee eee Linking Code for Non OS 9 Systems 0 2000 ee ee eee OS 9 Programming Chapter 7 Techniques Rules for Programming Techniques 0 cece eee eee eee Program and Data Memory References 000 cee eeeee Data Area References 0 00 ccc ccc cee ee cece eee eee as Code Area References celle nh Example Program Appendix A Example Program 2 0 cece cee rn A 1 Assembler and Linker Appendix B Error Messages Assembler Error Messages 000 cece eee eee B 1 Linker Error Messages lessen B 3 The Assembler Rdump Basic Information About Assembler The assembler r68 permits sections of assembly language source programs to be independently translated to Relocatable Object Files ROF s Global and local variables and program statement labels can be declared or referenced in each source program section The assembler s macro facilities permit commonly used statement sequences to be defined then used freely within the program w
28. OO 1000 OxFFFF 3 0300 OxDEADFACE Binary Numbers A percent sign 96 followed by one to sixteen binary digits 0 or 1 For example 0101 10101010 1111000011110000 Chapter 1 Basic Information About Assembler 1 8 Floating Point Numbers Specify floating point numbers in the following format the exponent may be specified with either an upper or lower case e digits digits e digits The range for floating point numbers is 2 2 10 308 to 1 8 104308 For example ds TORS le5 SCOR 4 106352 671e4 123456789 Character Constants A single character enclosed by single quotes For example Xx To ror Symbolic Names One to nine characters consisting of Character Description upper or lower case letters A Z az digits 0 9 Special characters underscore at sign the dollar sign period The first character cannot be a digit a dollar sign or a period Symbolic names ending with a 68020 legal size specifier can cause ambiguities in the 68020 extended addressing modes For example to distinguish the label maxval l from the symbol maxval with the size attribute of long use maxval l Location Counter Symbols The asterisk and period characters are two special symbols that represent the assembler s internal location counters The asterisk character represents the value of the current location counter before the i
29. S 9 to dynamically add or remove modules from a process memory space PIC allows OS 9 to load a program at any address where free memory is available Absolute addressing should never be used Fortunately the 68000 instruction set is generally well suited for writing PIC PIC programming techniques require that only program counter relative PCR addressing modes be used to access the program object code area The bsr Bec and DBcc instructions do this inherently Notice that the 68000 addressing scheme does not allow an operand addressed as PCR to be modified This enforces the OS 9 design philosophy that no program should modify itself 7 4 Chapter 7 05 9 Programming Techniques When addressing constants constant tables or addresses of routines within the program object code the PCR addressing modes d PC and d PC Xi can only be used on instructions that do not alter their objects Directly stated PCR addressing modes can never appear as a destination address or as an address of data to modify The 68000 addressing modes themselves discourage self modifying programs The lea and pea instructions can be used with PCR addressing modes to obtain actual addresses within the program area at run time For example to obtain the address of a constant table the following instruction can be used lea table PC a2 The offset in the PCR addressing mode is limited to a 16 bit signed value This limitation restricts the use of this ad
30. This statement must not have label or comment fields Options Option Description Ic Prints a listing of conditional assembly lines in an assembler listing Default off d lt num gt Sets the number of lines per page to lt num gt for a listing Default 66 le Prints errors Default on f Uses form feed for page eject instead of line feeds Form feed for top of form Default off g Lists all code bytes generated Default off n Omits line numbers from the assembler listing This allows more room for comments Writes a formatted assembler listing to standard output If not used only error messages are printed Default off m lt num gt Specifies the microprocessor that the assembler is to be used with 0 68000 68020 Default o lt path gt Writes the relocatable output to the specified mass storage file h Quiet mode Suppresses warnings and nonfatal messages s Prints the entire symbol table at the end of the assembly listing Default off k Prints macro expansion in assembler listing Default off 4 7 Chapter 4 Assembler Directive Statements pag Spc 4 8 Begin New Page in Listing Put Blank Line s in Listing Syntax pag e spc expression Function pag and spc improve the readability of program listings They are not printed They cannot have labels pag causes the assembler to begin a new page of the listing spc puts
31. all code segments which when processed by the linker form the final executable memory module Each code segment is called a psect The psect is the module unit with which the linker operates The psect provides the following information to the linker the identifying information about the psect the size of the code data initialized data and remote memory area the symbols defined by the individual psect the symbols referenced by the psect relocation information the actual code and initialized data The root psect is the psect from which all other references are resolved The file containing the root psect must be named first on the 168 command line The root psect is distinguished from other psects by the appearance of a non zero type language field in the psect directive of the source file AII other psects processed in the linkage must have a zero type language field The psect directive in the root psect provides the linker with the name of the psect and prototype module header information The type language attribute revision edition number stack requirement module entry point offset and uninitialized trap handler entry offset appear in the psect directive They are used to set up the corresponding entries in the module header Many of these values can be altered by using linker command line options 6 1 Chapter 6 The Linker The Subroutine Psect The Linker Execution 6 2 A zero type language field
32. allis a built in macro to generate user trap calls User traps are used to access the OS 9 standard library modules cio and math or user written trap handlers tca11 has two arguments a vector number zero through 15 and a function code The output is equivalent to the instruction sequence trap lt vector gt dc w function For example the following tcall is used to access the double precision floating point comparison in the math module tcall TSMath TSDCmp Important tca11 0 is the equivalent to the os9 statement Understanding the Linker The Root Psect The Linker The linker 168 transforms the r68 assembler output into a single OS 9 format memory module A memory module must minimally consist of a module header a module body and a cyclic redundancy check CRC Many modules require more than this basic information Program and Trap Handler Modules for example require a data memory requirement and stack memory requirement File manager device driver and device descriptor modules all require special information unique to each The contents of the assembly language relocatable output files ROFs provide the linker with the information required to create each type of memory module The linker allows references to occur between modules in order for one module to reference a symbol in another module This involves adjusting the operands of many machine language instructions A program usually consists of many sm
33. am that you can run from the shell from a shell procedure file etc The file and memory module names are r68 The r68 command line syntax is r68 file name lt option s gt Important 68020 is the name for the respective command program used with the 68020 assembler The syntax for r68020 is the same as above The file name can be followed by an option list This allows you to control various factors such as object file or listing generation listing format control etc An option list contains one or more options separated by spaces or commas An option is turned on by its presence in the list preceded by a hyphen Two hyphens followed by an option turns off the function If an option is not expressly given the assembler will assume a default condition for it Important Some command line options can be overridden by an opt statement within the source program By default the output of r68 is directed to the standard output path usually the terminal display It may optionally be redirected to another pathlist such as a printer a disk file or a pipe to another program Output redirection is handled by the shell and not the assembler itself r68 automatically handles memory allocation for its working data area Most of the data area memory is needed for the symbol table x68 will request memory as needed up to the maximum available memory The following are typical r68 command lines They are functionally ide
34. an be reproduced at will Appendix B Assembler and Linker Error Codes Error Message Description operand size error This message occurs when an operand value exceeds the legal range for the size of the operand It is displayed with additional text such as 168 error operand size error The value of symbol funny 193 is too large for a byte operand The offending operand is at offset 13cl in the code area of psect main in Fine Cptsr In this case the value for the symbol funny is in hex 193 This value is too large to fitin a byte size operand The next line indicates where in the psect the operand appears In this case the operand appears at offset in hex 13c1 in the code area The location counter field on the assembly listing is the offset value Finally the offending psect name and the file in which the psect appears is displayed out of memory The linker cannot obtain enough memory to do the linkage Memory usage requirements depend on many factors number of input files number of psects number of global sym bols and undefined references The largest use of memory is during the second pass when each psect s references must be adjusted for the final program module To do this step the linker must be able to get as much memory as the largest psect used A psect thatis 128k long requires a 128k buffer to link This is an internal linker error This is caused by information from the assembler that th
35. at is given only FPCR FPSR orFPIAR are allowed If x is given only FPO FP7 are allowed Program Control Instructions Mnemonic Format Syntax Description fbcc label Branch on floating condition fdbcc Dn lt label gt Decrement and branch on floating condition fnop No operation fscc lt ea gt Set on floating condition ftst lt ea gt Test floating operand This instruction uses floating point condition predicates for cc System Control Operations Mnemonic Format Syntax Description frestore lt ea gt Restore internal state fsave lt ea gt Save internal state ftrapcc lt data gt Trap on floating condition This instruction uses floating point condition predicates for cc Chapter 1 Basic Information About Assembler The fsincos instruction is a special dual monadic instruction Consequently two operands are given Mnemonic Description fsincos bwlsdx ea FPc FPs Simultaneous Sine and Cosine X FPm FPc FPs FPc is the resulting cosine value FPs is the resulting sine value Floating Point Condition Predicates used for CC Mnemonic Description EQ Equal F False GE Greater than or equal GL Greater or less than GLE Greater less or equal GT Greater than LE Less than or equal LT Less than E ot equal GE ot greater tha
36. ating Point Examples Example Description fadd 10 fp0 Long integer value of 10 is converted to extended and added to fp0 fadd l 0x10 fp0 Same as above fadd s 5 fp0 Single precision value of 5 is converted to extended and added to fp fadd s 0x40A0 fp0 Same as above fadd d 1 3e4 fp0 Double precision value of 130000 is converted to extended precision and added to fp0 fadd d 0x40C 964 fp0 Same as above fadd x 0x3ff fp0 Extended value of 3FF000000000000 is added to fp0 Floating point expressions are not supported Chapter 1 Basic Information About Assembler The 68881 instruction mnemonic summary uses the notation Notation Description lt data gt Immediate data of appropriate size lt ea gt Any legal addressing mode for the instruction In the 68881 instruction mnemonic summary the following format describes the instructions Mnemonic Format Syntax Description lt inst gt b w l s d or x lt syntax gt lt description of instruction gt For example fadd b w l s d X ea FPn Add X FPm FPn The example above describes the fadd instruction It shows that the fadd instruction may take the form fadd b fadd w fadd l etc and use the syntax lt ea gt FPn fadd x however may use the syntax FPm FPn For example fadd x fp0 fpl fadd x 5 f p0 Dyadic Instructions Dyadic floating point instructions require two source operands The first sour
37. ce operand can be any effective address or a floating point register The second source operand must be a floating point register The results of the operation are stored in this same register The general format of the dyadic instructions is as follows Mnemonic b w l s d X X lt ea gt FPn FPm FPn lt dyadic inst gt 1 21 Chapter 1 Basic Information About Assembler 1 22 The following 68881 floating point instructions use the above dyadic syntax Mnemonic Description add Ad fcmp Compare fdiv Divide fmod Modulo remainder fmul Multiply frem IEEE remainder fscale Scale exponent fsgldiv Single precision divide fsgimul Single precision multiply fsub Subtract Monadic Instructions Monadic floating point instructions require only one source operand These instructions can specify a source and destination operand The source operand can be any effective address or a floating point register The operation is performed on the source operand and the result is placed in the destination operand which is always a floating point register If the source operand is an effective address any operand format can be given If the source operand is a floating point register only the x format is allowed If no destination floating point register is given the operation is performed on the given register and the resulting value is stored in the same register The general format
38. cessed within a vsect A beginning or ending quotation mark was expected but not found Linker Error Messages Appendix B Assembler and Linker Error Codes The following is a comprehensive list of the error warning and informational messages issued by the OS 9 68000 linker 168 In this section the following syntax conventions are used a lt file gt Represents the actual file name in questions lt n gt Represents the actual number in question lt char gt Represents the actual character in question The following table lists Linker error messages and a description of each message Error Message lt file gt contains a 6809 module lt file gt contains assembly errors lt file gt contains no root psect this linker lt file gt is not a relocatable module lt file gt rof lt 4 and code 32k Must be re assembled bad syscrc size can t create output file can t create symbol file can t open lt file gt can t open lt file gt name file can t reopen input file lt file gt lt file gt created by assembler too new for Description A module from the 6809 assembler was encountered A module was encountered that had assembly errors Fix the errors and re link The first file given on the command line must contain a root psect A root psectis the psect from which all references are resolved A root psect is specified by non zer
39. ch more efficient and flexible use of system memory than in other operating systems In order for these techniques to work properly you must follow certain rules when writing assembly language programs Programmers who use only high level languages such as C BASIC Pascal etc need not be as concerned with these rules because the compilers automatically carry them out The key to being able to effectively use these methods is to have a good knowledge of the environment OS 9 provides for programs and also the instructions and addressing modes of the specific processor RULE 1 All executable code must be in memory module format The OS 9 memory module is the basis of both memory management and the advanced modular programming techniques the operating system supports The assembler and linker automatically generate the module header and CRC check values For detailed information concerning memory modules see the OS 9 Technical Manual RULE 2 Program and data areas must be separate All object code for a program is located in a memory module which is read only Programs should never modify themselves Therefore a separate memory area is used for variables Every process has a unique data area Every process does not necessarily have a unique program memory module This allows two or more tasks to share the same copy of a program if they are running the same program This technique is an automatic function of OS 9 that results in efficient u
40. ctions involving a PCR reference to be directed through the jump table OS 9 programs commonly use the lea instruction to determine the address of a table or in the case of a C program a function Often this instruction cannot address its destination because of the range limit In this case each lea instruction that does not reach its destination address is replaced by a move which references the destination address appearing in the jump table For example an out of range lea lea fprintf pcr a0 would be replaced by move l jmptbl1 8 a6 a0 An out of range pea pea fprintf pcr a0 would be replaced by move l jmptb1 8 a6 sp Only one jump table entry is created for each unique unreachable destination regardless of the number of times a destination could not be reached This allows resolution of the reference without changing the size of the code Both the original code and the substitute code are four bytes long Appendix Example Program The following example is the assembly language program UpDn a program that converts the case of input to either upper or lower This program is provided to give an example of the form and structure of an assembly language program nam UpDn ttl OS 9 68000 Example Assembly Prog ck ck ck Ck ck Ck ck Ck ck ck Ck ck ck ck ck kk ck ko ck ko ko kv kx Sk kv ko ko ko ko This program converts characters from upper case to lower case default 00000001 00000101 00008000 00
41. ddressing mode is only 8 bits signed which renders it useless for this purpose The index register however can be loaded with a 32 bit constant representing the offset to the data This method yields a 4 2 gigabyte unsigned offset 7 3 Chapter 7 05 9 Programming Techniques There are two basic ways of accessing remote variables Thie first method involves moving the 32 bit offset into a register and then using that register as an index from the data memory pointer a6 vsect remote bigone ds l 100000 declare a very large array ends move l bigone d0 get offset into bigone add 1 d4 d0 add subscript move l 0 a6 d0 1 d2 get the array value The second method involves copying the data pointer to a temporary address register and then adding the 32 bit offset to the temporary register It can then be used in simple Register Indirect addressing mode to access the remote variable For example the address of bigone can be determined by move l a6 a0 get the base address of the data adda l bigone a0 add in the offset to bigone move l a0 d2 get the array value Code Area References Many of OS 9 s capabilities are due to the use of memory modules All OS 9 object code must be in memory module format Use of memory modules is simple because 168 automatically generates them Another important requirement for OS 9 object code is position independence Use of position independent code PIC is essential It allows O
42. dressing mode to destinations within 32K of the reference Because many non trivial programs easily exceed this limit the linker provides a facility to overcome this limitation The a option of the 168 linker causes the linker to direct certain PCR references to a jump table in the data area For each bsr instruction that does not reach its destination address the linker will replace the bsr instruction with a jsr instruction The destination of this instruction references a jump table The linker creates the jump table as initialized data the size of which is added to the total initialized data allocation for the program Each jump table entry is an absolute long jmp instruction whose destination is initially an offset from the beginning of the program module to the reference The relocation information placed in the module by the linker is then used by the kernel to adjust the offsets in the jump table to reflect the absolute address of the actual reference Only long 16 bit offset bsr instructions are affected All other branch style instructions Bcc DBcc etc are still limited to the 32K restriction The following is an example of a modified bsr instruction Consider the jump table fragment jmptb1 0 jmp printf jmptb1 6 jmp fprintf jmptbl 12 jmp sprintf Chapter 7 05 9 Programming Techniques An out of range bsr bsr fprintf is replaced by jsr jmptbl 46 a6 The a option also causes lea and pea instru
43. ds The label field begins in the first character position of the line Labels are required by some statements equ and set Labels are not allowed on others for example assembler directives such as spc ttl etc The first character of the line must be a space or tab if the line does not contain a label If the label is present the assembler defines it as the address of the first byte of where the instruction s object code will be assigned The exceptions to the rule are labels on set and equ statements These are assigned the operand field value When a symbolic name in the label field of a source statement is followed by a colon the name is known globally by all modules that are linked together Because the label is known globally a branch or jump can be done to a location in another module For a global variable the data offset can be referred to by other modules If no colon appears after the label the label will be known only in the psect where it is defined Care must be taken to access the labels in the appropriate context The label must be a legal symbolic name consisting of from 1 to 256 uppercase or lowercase characters decimal digits the dollar period or underline _ characters The first character may not be a dollar sign period or digit Upper and lower case characters are distinct Labels and names in general must be unique They cannot be defined more than once in a program except when used wi
44. e pt r ALLEN BRADLEY NL 394 ROCKWELL INTERNATIONAL COMPANY With offices in major cities worldwide WORLD EUROPE MIDDLE HEADQUARTERS EAST AFRICA Allen Bradley HEADQUARTERS 1201 South Second Street Allen Bradley Europa B V Milwaukee WI 53204 USA Amsterdamseweg 15 Tel 414 382 2000 1422 AC Uithoorn Telex 43 11 016 The Netherlands FAX 414 382 4444 Tel 31 2975 60611 Telex 844 18042 FAX 31 2975 60222 Publication 1771 6 5 106 December 1992 As a subsidiary of Rockwell International one of the world s largest technology companies Allen Bradley meets today s challenges of industrial automation with over 85 years of practical plant floor experience More than 13 000 employees throughout the world design manufacture and apply a wide range of control and automation products and supporting services to help our customers continuously improve quality productivity and time to market These products and services not only control individual machines but integrate the manufacturing process while providing access to vital plant floor data that can be used to support decision making throughout the enterprise ASIA PACIFIC CANADA LATIN AMERICA HEADQUARTERS HEADQUARTERS HEADQUARTERS Allen Bradley Hong Kong Allen Bradley Canada Allen Bradley Limited Limited 1201 South Second Street Room 1006 Block B Sea 135 Dundas Street Milwaukee WI 53204 USA View Estate Cambridge Ontario NIR Tel 414 382 2000 28 Watson Road
45. e rod lt ea gt Rotate without extend memory roxd s Dx Dy Rotate with extend register roxd s lt data gt dy Rotate with extend immediate roxd lt ea gt Rotate with extend memory rte Return from exception rtr Return and restore condition codes rts Return from subroutine rtd lt dis placement gt Return and deallocate rtm Rn Return from module sbcd Dy Dx Subtract decimal with extended register Sbcd Ay Ax Subtract decimal with extended memory cc in the following instruction represents the branch condition code Mnemonic SCC ea Description Set according to conditional registers stop data Load and stop sub s lt ea gt Dn Subtract binary register sub s Dn lt ea gt Subtract binary memory Suba s lt ea gt An Subtract address w or l subi s lt data gt lt ea gt Subtract immediate Subq s lt data gt lt ea gt Subtract quick subx s Dy Dx Subtract with extend register swap Dn Swap register halves tas lt ea gt Test and set operand trap lt vector gt Trap trapv Trap on overflow In the following three instructions Mnemonic cc uses standard condition codes Description Trap on Condition trap cc trap cc w lt data gt Trap on Condition trap cc lt data gt Trap on Condition tsts ea Test operand unlk An Unlink unpk Ax Ay adjust Unpack BCD unpk Dx Dy adjust
46. e limited only by the available contiguous system memory When ds is used the uninitialized data location counter is used When a remote vsect is in effect the ds applies to the remote data location counter The dc and dz directives are used to set initial data values The assembler uses the initialized data location counter for these directives The constants appear in the data area of the program when executed These values can then be modified 1f desired The dc and dz directives can also appear outside of a vsect in the body of the psect In this case the constants are assembled into the code area of the program Do not change constants defined in this manner To do so would cause the program to be self modifying and non re entrant Important The data location counters maintain their values from each vsect block to the next Because the linker handles the actual data allocation there is no facility to adjust the data location counters The object code output by the assembler must be processed by the linker before the code is executable The assembler writes the object code in a special relocatable object file format ROF to allow the linker to link together separately assembled modules into a single executable module The ROF contains information such as the global data definitions code entry points external references actual object code and initialized data Chapter 3 Relocatable Program Sections 3 8 It is unlikel
47. e linker does not expect If this happens be sure the assembler and linker are properly installed on the system from the original distribution medium Contact Microware if this error can be reproduced at will reference location error n root psect found in both lt filel gt and lt file2 gt Only one root psectis allowed for a program A root psectis defined as a psect in which the Type Language field is non zero The root psect is the initial psect from which all external references are resolved symbol name not found during pass 2 This is an internal linker error Contact Microware if this error can be reproduced at will too many data references lt n gt This is an internal linker error Contact Microware if this error can be reproduced at will unknown option lt char gt An option given is not an option recognized by the linker unknown reference type lt n gt This is an internal linker error Contact Microware if this error can be reproduced at will unresolved references The symbols previously listed by the linker are not defined by a psect given on the command lines or in libraries This is commonly caused by improperly ordered library files See Chapter 6 and the discussion of Linker Library Files for details on library searching Additional error messages such as the following normally appear previous to this message Symbol funny unresolved Referenced n times by psect main in fil
48. e6 b27c 00ea 6602 00ec 7200 00ee 24e40 000000 2 PrsOpt10 PrtHelp PrsOpt20 UpDn10 UpDn20 UpDn80 UpDn90 UpDn99 dbra bra s moveq lea move l os9 bra s subq w bcs s move b eori b andi b bne s move w bra s moveq moveq lea os9 bcs s move b cmp blo cmp bhi eori b non o moveq moveq os9 bcc s cmp w bne s moveq os9 ends d5 PrsOpt until no more option bytes UpDn10 StdErr d0 standard error path HelpStr pc a0 help message string HelpLen dl length of string ISWritLn output help message UpDn90 exit 1 d5 decr option cnt PrtHelp abort if end of parameters a5 d0 get option character ru pado is ita u Option a A d0 ignore case difference PrtHelp abort if not az LowBound a6 reset convert bounds PrsOpt10 check for other options StdIn d0 from standard input 1 d1 read one character Char a6 a0 inta Char ISRead UpDn80 abort if error Char a6 d0 get character LowBound a6 d0 in range UpDn20 branch if not HiBound a6 d0 in range UpDn20 branch if not d a A Char a6 convert characters case StdoOut dod to standard output 1 d1 write the character ISWritLn UpDn10 repeat if no error ESEOF dl end of file error UpDn99 abort if not 0 d1 return without error FSExit exit Assembler Error Messages Error Message Bad label Bad Mnemonic Bad number Bad operand
49. ecutable Memory Module Generated by 168 5 odule Header Mainline segment gt Segment A Object Code Segment B Object Code Segment C Object Code Initialized Data Information Generated by 68 gt CRC Check Value Figure 3 2 Process Data Area Segment A Uninitialized Variables Segment B Uninitialized Variables Segment C Uninitialized Variables SegmentA Initialized Variables Segment B Initialized Variables Segment C Initialized Variables Segment A nitialized Remote Variables Segment B nitialized Remote Variables Segment C nitialized Remote Variables SegmentA U ninitialized Remote Variables Segment B U ninitialized R emote Variables Segment C U nnitialized Remote Variables 3 2 These correspond to each segment s psects These correspond to each segments vsects These correspond to each segments remote vsects Program Section Declarations Psect and Vsect Chapter 3 Relocatable Program Sections Most program statements are included in sections called psects and vsects program and variable sections respectively A psect contains the program instructions and variable declarations Each source file may have only one psect Global symbols labels with a colon suffix in this section are accessible from all other program segments Similarly statements
50. ed against the A6 register these labels yield the address of the desired data Because the offset is limited by the hardware addressing mode to a 16 bit signed value the offset can address only 32K To fully use the 64K range that an unsigned offset would provide the linker automatically starts assigning the data storage offsets from 8000 When OS 9 assigns data memory for a process the A6 register is automatically adjusted to point 32K past the actual base of the data memory This method allows a full 64K of addressability from the Register Indirect with Offset addressing mode The 32K data memory base adjustment is done only for user state program and trap handler modules No adjustment is made for system state modules such as device drivers or file managers The total size of the initialized and uninitialized data memory cannot exceed 64K To do so would cause the memory beyond 64K from the base pointer to be unaddressable with the Register Indirect with Offset addressing mode The following is an example of referencing the initialized and uninitialized data areas vsect varname ds l 1 an integer variable counter dc l1 500 an integer variable initialized to 500 ends move l varname a6 d0 access the uninitialized data memory cmp l d0 counter a6 access the initialized data memory The only way to offset beyond the 64K data memory limit is to use the Indexed Register Indirect with Offset addressing mode The offset for this a
51. ent value of the offset counter The offset counter is then incremented by the result of the expression multiplied by 1 for a byte 2 for a word or 4 for a long When an lo statement is encountered the offset counter is decremented by the appropriate size and the result is assigned to its label This is useful in conjunction with the 68000 link instruction org Sets or changes the origin starting value of the offset counter Example 1 is the same as joe equ 500 1 moe equ 504 do b 1 Gives label A the value of its ASCII code do b 1 Gives label B the value of its ASCII code do b 1 Gives label C the value of its ASCII code do b 1 Gives label D the value of its ASCII code do b 1 Gives label E the value of its ASCII code 5 7 Chapter 5 Pseudo Instructions os9 tcall 5 8 Call OS9 System Call Syntax os9 expression Function os9 is a convenient way to generate OS 9 system calls Its operand is a word value to be used as the request code The output is equivalent to the instruction sequence trap 0 dc w expression System symbolic names are available in the sys l system library file These names are commonly used with the os9 statement to improve the readability portability and maintainability of assembly language software Examples os9 I Read Calls OS 9 READ service request os9 FSExit Calls OS 9 EXIT service request Generate User Trap Call Syntax tcall vector function Function tc
52. er of zero values to be placed in the appropriate code or initialized data section Under OS 9 it is unnecessary and undesirable to reserve zero bytes in the initialized data area vsect The data area is automatically zeroed by the fork system call so a dz in the vsect only wastes space in the object code area A dz used within a psect is used to create a read only zero constant that should not be changed by the program A dz used within a vsect is considered as initialized data that can be altered by the program Examples dz b 24 Reserve 24 zero value bytes dz w 1 Reserve 1 zero value word do lo org org joe moe org Ej O OQ Uo 500 do 1 do 1 LA Chapter 5 Pseudo Instructions Assign Offset Counter Value to Label Decrement Offset Counter Then Assign Value to Label Set Offset Counter Origin Syntax label do s expression label lo s expression org expression The size extension s can be b for bytes W for words default for longwords Function do and 1o are used to assign an increasing or decreasing set of values to a set of symbolic names respectively It has nothing to do with memory allocation Many times it is desirable to define a group of names with sequentially related values Some examples are error codes character sets and stacked variables do and 1o provide a convenient means of doing this Each time a do is encountered its label is given the curr
53. errors When writing condition assembly ensure that the conditional evaluates to the same value during the first and second pass or phasing errors are likely to result The ifdef and ifndef directives are useful for assembling sections of code based on the presence of a symbol ifdef and ifndef are most useful when symbols are defined on the command line This allows makefiles to pass symbols affecting the assembly without actually changing any definitions in a file 4 5 Chapter 4 Assembler Directive Statements nam ttl 4 6 Rename Program Rename Listing Title Syntax nam string ttl string Function nam Specifies the program name that is printed in a program listing tt1 specifies the title line that is printed in a program listing These statements cannot have label or comment fields The program name is printed on the left side of the second line of each listing page followed by a dash then by the title line The name and title may be changed as often as desired Examples nam Datac ttl Data Acquisition System Generates Datac Data Acquisition System Chapter 4 Assembler Directive Statements opt Set Assembler Options Syntax opt lt option gt Function opt allows any of several assembler control options to be set or reset Options are denoted by a single character A preceding hyphen turns the specified option off One exception is the d option which must be followed by a number
54. ers and file managers cannot have initialized data Initialized data is generated by the C Compiler when C initializers appear for static or global data Initialized data is generated by the assembler when a data initialization directive dc dz etc appears in a vsect jmp total gt guess lt n gt lt n gt This is an internal linker error Contact Microware if this error can be reproduced at Will no data storage allocation vsect allowed Only modules of type object code can contain data storage allocation Other module on non object modules types usually language runtime interpreters define data storage allocations in a different manner no initialized static data allowed on raw output Initialized data cannot be allocated to a program designed to run without OS 9 Uninitialized data is allowed The linker prints the size of the uninitialized data requirement for raw modules no root psect found The first module given on the command line must contain a root psect A root psect is a module in which the psect directive indicates a non zero type and language word A zero type and language word means a subroutine module The root psect is the psect from which all references are resolved non remote data allocation value exceeds 64k See the discussion in the manual on data area references for a description of the linker memory limits odd count for crc This is an internal linker error Contact Microware if this error c
55. ert Bit Field bfset lt ea gt offset width Set Bit Field bftst lt ea gt offset width Test Bit Field bkpt lt data gt Breakpoint bra label Branch word displacement bra s label Branch byte displacement bra b label Branch byte displacement bra w label Branch word displacement bra label Branch long displacement bsets Dn lt ea gt Test bit and set register b or l bsets data ea Test bit and set immediate b or I bsr label Branch subroutine word displacement bsr s label Branch subroutine byte displacement bsr b label Branch subroutine byte displacement bsr w label Branch subroutine word displacement bsr lt label gt Branch subroutine long displacement btst s Dn lt ea gt Test bit register b or l btst s lt data gt lt ea gt Test bit immediate b or l callm lt data gt lt ea gt Call Module cas Dc Du lt ea gt Compare and Swap with Operand cas2 Dcl Dc2 Du1 Du2 Rn1 Rn2 Compare and Swap with Operand chk lt ea gt Dn Check register against bounds chk ea Check register against bounds chk2 s lt ea gt Rn Check register against bounds b w or l clr s ea Clear operand cmp s lt ea gt Dn Compare data register cmpa s lt ea gt An Compare address register cmpi s lt data gt lt ea gt Compare immediate cmpm s Ay Ax Compare memory
56. evice On OS 9 6809 systems for 68000 cross compilation these directories should be called dd DEFS 68K and dd LIB 68K For UNIX systems new directories should be created for the cross software on the root device user and user bin The macro assembler files should then be copied to user bin user bin should be added to the shell program search list so that OS 9 cross file names do not conflict with other UNIX file names The DEFS and LIB directories should be created within the user directory for example user lib and user defs This manual covers both the 68000 and 68020 assembler and linker The 68020 assembler can process all 68000 instructions and syntax However there is a superset of 68020 instructions Because of this discrepancy all items specific to the 68020 assembler linker or debugger are shown in shaded boxes for easy reference All other text references both the 68000 and 68020 programs All references to OS 9 68000 or 68000 code includes 68020 unless specifically disclaimed Table of Contents Basic Information Chapter 1 About Assember The Assembler 0 0 0c ccc cee cee ee eee RR hh RGUMP 645 borin condos UE The Assembly Language Program Development Process Runnmng TOS ere esa eer ea pex oe x ear o acp E et Cn els r68 Options ss ce pedan bu ner Reed dace ed RR re EGRE Input File Format er ope RT RUE LI Rin pe IR Evaluation of Expressions 0 0000 cece eee eh 6800
57. explained in detail in the following table Description The statement s label has an illegal character or does not begin with a letter A mnemonic was found in mnemonic field that was not recognized or was not allowed in the current program section The numeric constant definition contains a character that is not allowed in the current radix An operand expression is missing or incorrectly formed An arithmetic expression is incorrectly formed An option is unrecognized or incorrectly specified The opening or closing bracket is missing A problem was encountered opening an input file B 1 Appendix B Assembler and Linker Error Codes Error Message Can t open macro work file Comma expected Conditional nesting error Constant definition ENDM without MACRO ENDR without REPT Fail message File close error llegal addressing mode llegal external reference llegal index register llegal suffix Label missing acro arg too long acro file error acro nesting too deep ested MACRO definitions ested REPT ew symbol in pass two o input files 0 param for arg Phasing error Redefined name Symbol lost Too many args Too many object files Undefined org Unmatched quotes Description A problem was encountered opening a macro work file A comma was expected but not found A mismatched iffelse endc conditional assembly directive was found A constant definition is incorrectly formed A
58. f else endc Conditional Assembly Syntax ifxx expression statements else statements endc Function The ifxx statements provide conditional assembly capabilities This is the ability to selectively assemble specific parts of a program depending on a variable or computed value A single source file could therefore selectively generate multiple versions of a program Conditional compilation uses statements similar to the branching statements found in high level languages such as Pascal and BASIC ifxx uses a symbolic name or an expression as an operand A comparison is made with the result If the result of the comparison is true statements following the if statement are processed Otherwise the following statements are not processed until an endc or else statement is encountered For example the following ifeq statement compares the value of its operand to zero ifeq switch Assembled only if switch 0 endc The else statement allows the if statement to explicitly select one of two program sections to assemble depending on the truth of the if statement Statements following the else statement are processed only if the result of the comparison is false For example ifeq switch Assembled only if switch 0 else Assembled only if switch does not 0 endc Chapter 4 Assembler Directive Statements The endc statement marks the end of a conditionally assembled program section Multiple if s
59. f the reference Bit 7 Negative Reference If set this tells the linker to add the negative of the symbols location when resolved What Are Directive Statements end Assembler Directive Statements Assembler directive statements give the assembler information that affects the assembly process but usually do not cause code to be generated Read the descriptions carefully Some directives require labels labels are optional on others and a few directives cannot have labels End Program Syntax end Function end indicates the end of a program Its use is optional If not present in the source file end is assumed upon an end of file condition end statements may not have labels 4 1 Chapter 4 Assembler Directive Statements equ Assign Value to Symbolic Name set Syntax label equ expression label set expression Function equ and set assign a value to a symbolic name the label and thus require labels The value assigned to the symbol is the value of the operand which may be an expression a name or a constant You can use them in any program section Two differences exist between the equ and set statements Symbols defined by equ can be defined only once in the program Symbols defined by set can be redefined again by subsequent set statements The equ statement label name cannot have been defined previously The operand cannot include a name that has not yet been defi
60. imes in one command line to specify multiple library files Library files are searched in the order given on the command line The standard definition files are sys for assembly language or clib for the C compiler Mz mem k Adds mem K to the stack memory allocation m Prints the linkage map indicating the base addresses of the psects in the final object module n lt name gt Uses lt name gt as the module name 0 lt path gt Writes linker object memory module output to the specified file relative to the execution directory The last element in lt path gt is used as the module name unless overridden by the n option 6 6 Linking Code for Non OS 9 Systems Chapter 6 The Linker Option Description O lt path gt Writes linker object memory module output to the specified file relative to the data directory The last element in lt path gt is used as the module name unless overridden by the n option p lt n gt Sets the permission word in the module header to lt n gt lt n gt must be hexadecimal r Outputs a raw binary file for a non OS 9 target system The output will not be in memory module format r lt n gt Outputs a raw binary file for non OS 9 target systems with an object code base address at absolute address n n must be a hexadecimal address The base address is used to make absolute addressing references operate correctly S Prints a list
61. important and useful programming tool that can significantly extend r68 s capabilities In addition to creating instruction sequences you can also use them to create complex constant tables and data structures Chapter 2 Macros Macro Structure 2 2 document them Macros can impair the readability of a program if they are used indiscriminately and unnecessarily This can make it extremely difficult to understand the program logic ATTENTION When you use macros you should carefully A macro definition consists of three sections name macro the macro statement assigns a name to the macro body the macro body contains the macro statements endm the endm statement indicates the end of the macro The macro name must be defined by the label given in the macro statement The name can be any legal assembler label You can redefine the 68000 instructions themselves by defining macros having identical names This gives r68 the capability to be used as a cross assembler for non 68000 processors by definition and or redefinition of the instruction set of the target CPU ATTENTION Redefinition of assembler directives such as ds can have unpredictable consequences The body of the macro can contain any number of legal r68 instructions or directive statements including references to previously defined macros The last statement of a macro definition must be endm The text of macro definitions are stored on a temporary
62. in the psect directive indicates a subroutine psect These psects are usually subroutines that provide supporting code for the root psect Linker library files are simply separately assembled psects merged together into a single file Except for the psect name and stack size reservation fields all fields in the psect directive are zero When a program is being assembled the assembler does not know the addresses of names which are external references to other program sections For example the bsr instruction to a label in another program section cannot have its offset computed because the address of the destination label is not known until all sections are combined by the linker Therefore when an external reference is encountered the assembler sets up information in the ROF which identifies the instructions that reference external names Because the assembler is not aware of what the actual offset within the module will be each section is assembled as though it starts at offset 0 The linker uses the ROFs produced by the assembler as input The linker reads all the ROFs and then assigns each ROF a relative starting offset for its data storage space and a relative starting offset for its object code space Important Because OS 9 requires programs to be position independent code with separate position independent data areas these addresses remain relative OS 9 assigns these physical memory areas when a program is loaded and executed The
63. internal buffer The reference list in the psect is read to determine the locations of all operands referencing external symbols These operands are then adjusted to reflect the destination s position in the output module 6 3 Chapter 6 The Linker Linker Library Files 6 4 If the a option is used and the reference cannot reach the destination with the 16 bit offset addressing mode the reference is changed to reference a jump table entry The code and initialized data segments are then written to the output file As each segment is written out the OS 9 module CRC is calculated The CRC is then written into the output module when all psects have been processed Library files are created by concatenating one or more ROFs into a single file To change a single psect in a library file the entire library must be re created from the ROFs substituting the new psect for the old The linker performs only one pass over the input files to locate symbol definitions Because of this the order in which the psects appear in the library file is very important The psects must be ordered so that the references are generally forward references Consider the following example psect main_c defines main references sub 1 psect subl c defines sub 1 subla references sub2 psect sub2 c defines sub2 references printf The psect sub1_c must appear in the library before any psect containing a symbol that sub1_c refe
64. ith appropriate parameter substitution x68 also supports conditional assembly and inclusion of library source files r68 is a two pass assembler During the first pass through the source program the symbol table is created by scanning each line in order to identify symbolic name definitions During the second pass machine language instructions and data values are placed in the relocatable object file The linker combines previously assembled relocatable object files in a separate pass The linker 168 takes any number of program sections and or library sections and combines them into a single executable OS 9 program Global data and program references are automatically resolved during the linking process The output of the linker is a binary executable file in the standard OS 9 memory module format The linker also generates the appropriate module header for the program Important For detailed information about memory modules refer to the OS 9 Technical Manual rdump is a program you can use to examine the contents of library files The syntax for rdump is rdump lt rof gt lt opts gt lt rof gt must be a relocatable object file library It usually has a suffix of ror Jl Chapter 1 Basic Information About Assembler The rdump options are Option Description a Tums onall options displays global symbols local relocation information and external references g Displays the defined global
65. larify the following discussion segments are synonymous with source files OS 9 processes use at least two separate areas of memory the program object code in memory module format and a data area used for the program s variables and the stack The linker 168 combines all of the segments into a single OS 9 memory module and a coordinated data storage area By using global symbolic names code in each segment can reference variables declared in other segments or may transfer program control to labels in other segments When the assembler source program for each segment is written it must be divided into distinct sections for variable storage definitions vsects and for program instructions psects The output of the assembler is a distinct relocatable object file ROF containing the object code output plus information about the variable storage declarations for the linker to use The linker reads the ROFs assigns space in the data storage area and combines all the object code into a single executable memory module As it does so it must alter the operands of instructions to refer to the final variable assignments and must also adjust program control transfer instructions that refer to labels in other segments For example if three segments called A B and C are processed by the linker the resulting memory allocation is shown in the simplified memory map below 3 1 Chapter 3 Relocatable Program Sections Figure 3 1 Ex
66. linker processes the input files in three phases During the first phase the linker reads all the input files in the order they appear on the command line Each psect is checked for validity The global symbol definitions are entered into the defined symbol table If a symbol of the same name already exists in the defined symbol table an error message is generated Each global symbol is then checked against the undefined symbol table If the global symbol defines an external reference the symbol is removed from the undefined symbol table Finally the reference list is examined to identify references to undefined symbols that are not yet in the undefined symbol table Any such symbols are then added to the undefined symbol table Chapter 6 The Linker After examining the input files the linker reads the library files They are processed using the same procedures as used for input files with minor exceptions A psect appearing in a library file is retained for the final module only if the psect defines an as yet undefined symbol After each psect in a library file is processed the undefined symbol table is examined to see if any symbols are still undefined If so library file processing continues If not the next psect in the library file or the next library file is processed A symbol psect is handled as a special case by the linker It contains no code or data only symbols defining constants When a symbol psect is processed
67. lt num gt Specifies machine assembler to be used 0 68000 68020 Default n Omits line numbers from the assembler listing This allows more room for comments 0 lt path gt Writes the relocatable output to the specified file must be a mass storage file Default off q Suppresses warnings and nonfatal messages quiet mode Default off S Prints the symbol table atthe end of an assembly listing Default off V Displays assembler Version and Edition number on standard error path X Prints macro expansion in assembler listing Default off These options do not make sense unless the 1 option is also used Input File Format r68 reads the specified assembly source code file for its input Each line in the file is a text string terminated by an end of line return character The maximum length of an input line is 256 characters An input line is made up of one to four fields separated by spaces and or tabs The following fields may be used a label field optional an operation field an operand field containing 0 or more operands depending on the operation acomment field optional Important There are also two special cases An asterisk in the first character position indicates a comment line The entire line is printed in the listing but is not otherwise processed Blank lines are also included in the listing but are likewise ignored Chapter 1 Basic Information About Assembler Label Fiel
68. mediate andi lt data gt ccr And immediate to condition code andi lt data gt sr And immediate to status register In the following 3 instructions the shift direction d may be 1 for left or r for right Mnemonic Description asd s Dx Dy Arithmetic Shift register asd s lt data gt Dy Arithmetic Shift immediate register asd ea Arithmetic S hift memory Chapter 1 Basic Information About Assembler In the following instructions cc represents the branch condition code Mnemonic Description bcc lt label gt Conditional branch word displacement bcc s label Conditional branch byte displacement bcc b label Conditional branch byte displacement bcc w label Conditional branch word displacement bcc label Conditional branch long displacement bchg s Dn ea Test bit and change register b or bchg s 4 data ea Test bit and change immediate b or I belr s Dn ea Test bit and clear register b or I bclr s lt data gt lt ea gt Test bit and clear immediate b or l bfchg ea offsetwidth Test Bit Field and Change bfclr ea offset width Test Bit Field and Clear bfexts lt ea gt offset width Dn Extract Bit Field Signed bfextu ea offset width Dn Extract Bit Field Unsigned bfffo ea offsetwidth Dn Find First One in Bit Field bfins Dn ea offsetwidth Ins
69. mes The linker has determined that the same symbol name appears in more than one psect in the allocation of the final module Consider the following program fragment main strcat strlen return When compiled and linked linkage will fail and return the messages Symbol strlen defined by psect strings c in file dd lib clib 1 has already appeared in psect prog c in file ctmp 001543 r Symbol strcat from psect strings c in file dd lib clibn l caused name clashes Since both prog c and strings c define the symbol strlen the linker cannot resolve the reference to strcat without causing the definition of strlen to be ambiguous The first message indicates that strlen was defined in both prog c and string c The Second message identifies the symbol thatthe linker was attempting to resolve when it found the name clash error reading input file lt file gt The linker could not read the input file Either a physical error occurred or the input file was incorrectly formatted All input files must be output from the assembler error writing file lt file gt The linker could not write the output file Possible causes are disk errors or media full initialized data or jumptable allowed Initialized data is supported only for program modules entered by F F ork or trap only on program or trap handler modules handler modules entered by F TLink Modules such as system modules device driv
70. n endm was found with no matching macro An endr was found with no matching rept A fail directive was encountered A problem was encountered closing an input file The addressing mode cannot be used in the instruction External names cannot be used with assembler directives If an operand expression contains an external name the only operation allowed in the expression is binary plus and minus The register cannot be used as an index register An illegal suffix was found in an instruction This statement is missing the required label The Macro argument is too long No more than 60 characters total can be passed to a macro A problem was encountered accessing the macro work file The macro calls are nested too deeply Macro calls may only be nested up to 8 levels deep A macro cannot be defined inside a macro definition Repeat blocks cannot be nested See symbol lost An input file must be specified A macro expansion is attempting to access an argument that was not passed by the macro call A label has a different value during pass two than it did during pass one The name appears more than once in the label field other than on a set directive Assembler symbol lookup error The error could be caused by symbol table overflow or bad memory Too many arguments were passed to the macro No more than 9 arguments may be passed to a macro Only one o command line option is allowed program counter org cannot be ac
71. n or equal GL ot greater or less than GLE ot greater less or equal GT ot greater than LE ot less than or equal LT ot less than OGE Ordered greater than or equal OGL Ordered greater or less than OGT Ordered greater than OLE Ordered less than or equal OLT Ordered less than OR Ordered SEQ Signaling equal SF Signaling false SNE Signaling not equal ST Signaling true T True UEQ Unordered or equal UGE Unordered or greater or equal UGT Unordered or greater than ULE Unordered or less or equal ULT Unordered or less than UN Unordered Chapter 1 Basic Information About Assembler Constant ROM Table The following are offsets into the 68881 constant ROM that contain useful values Offset Constant 00 PI 0B Logio 2 0C e 0D Log e 0E Log o e 0F 0 0 30 n 31 nio 32 100 33 101 34 10 35 104 36 108 37 1016 38 1022 39 1064 3A 10128 3B 10256 3C 10512 3D 101024 3E 102048 3F 104096 Introduction to Macros Chapter Macros Identical or similar sequences of instructions may often be repeated in different places in a program Writing a sequence of instructions repeatedly can be tedious if the sequence is long or must be used a number of times A macro is a definition of an instruction sequence that can be used numerous places within a program The macro is given a name which is used similarly to any othe
72. ndition Explanation cc IC Carry clear cs C Carry set eq Z Equal ge N V4N IV Greater than or equal gt N V Z HN IV IZ Greater than hi IC Higher hs IC Higher or the same le Z N IV IN V Less than or equal lo C Lower ls C4Z Lower or the same It N IVUN V Less than mi N inus ne IZ ot equal pl IN Plus vC IV Overflow clear vs V Overflow set The following condition code bit symbols are used in the above table Symbol Description N negative V overflow Z zero C carry Chapter 1 Basic Information About Assembler The following instruction mnemonic summary uses these conventions Convention Description data Immediate data of appropriate size S Indicates w l or b The default is w if the size is not explicitly given ea Any legal addressing mode for the instruction Mnemonic Description abcd DyDx Add decimal with Extend Register abcd Ay Ax Add decimal with Extend Memory add s lt ea gt Dn Add binary register add s Dn lt ea gt Add binary memory adda s lt ea gt An Add address w or only addi s lt data gt lt ea gt Add immediate addq s lt data gt lt ea gt Add quick addx s Dy Dx Add extended register addx s Ay Ax Add extended memory and s ea Dn And logical register and s Dn lt ea gt And logical memory andi s lt data gt lt ea gt And im
73. ned as yet undefined names whose definitions also use undefined names Good programming practice dictates that all equates are at the beginning of the program equ is normally used to define program symbolic constants especially those used in conjunction with instructions set is usually used for symbols used to control the assembler operations especially conditional assembly and listing control cannot reference another equ that references an external name For example joe equ moe moe equ external ATTENTION set cannot reference external names equ Examples FIVE equ 5 OFFSE equ address base TRUE equ SFF FALSE equ 0 SUBSE set TRUE ifne SUBSET use subset defs else use full defs endc SUBSET set FALSE fail Chapter 4 Assembler Directive Statements Return Error Message Syntax fail lt textstring gt Function fail forces an assembler error to be reported lt text st ring gt is displayed as the error message which is processed in the same manner as r68 generated error messages Because the entire line following the fail keyword is assumed to be the error message this statement cannot have a comment field fail is most commonly used with conditional assembly directives that you set up to test for various illegal conditions especially within macro definitions Example ifeq maxval fail maxval cannot be zero endc Chapter 4 Assembler Directive Statements i
74. not be redefined or used out of context Register name Definition An Address register n Dn Data register n pc or pcr Program counter Sr Status register ccr Condition codes ssp Supervisor stack pointer usp User stack pointer Chapter 1 Basic Information About Assembler Register name Definition sfc Source function code dfc Destination function Cacr Cache control register vbr Vector base register caar Cache address register msp Master stack pointer isp Interrupt stack pointer The following definitions are used in addressing mode syntax Mode Definition Dn Data Register Direct An Address Register Direct Rn Data or Address R egister Direct Xn s Index Register n either address or data s indicates the index register size Itis either w word or long default An Address Register Indirect An Address Register Indirect with Postincrement An Address Register Indirect with Predecrement d An Address Register Indirect with Offset d An Xn s Address Register Indirect with Index xxx w Absolute S hort xxx Absolute Long d pc Program Counter Indirect with Offset d pc Xn s Program Counter Indirect with Index dox Immediate Data In the following definitions disp is an expression If disp is a symbol ending with w or l the parentheses are required to distinguish the symbol name from the size ex
75. nstruction assembled The location counter in use depends on the vsect psect block the assembler is currently processing If the current block is within a psect but not in a vsect contains the value of the code location counter If the current block is within a vsect contains the value of the non remote initialized data counter or the remote initialized data counter as specified by the vsect remote parameter For more information refer to the section on the VSECT directive OO OU C O Ox e E 00 08 Oa Oc 0e Chapter 1 Basic Information About Assembler The is often used in expressions to calculate distances For example 0000 Ibl 1 dc b 0 0 0 0 0 0 0 0 00000000 0000 fff8 lbl1 2 dc w lbl 1 distance from here to lbl 1 0004 1b1 3 dc w lbl 5 distance from here to lbl 5 fffe lbl 4 dc w bl 5 distance from lbl 5 to here 000e 1b1 5 dc w bl 1 distance from lbl 1 to here The period character is used to represent the current value of the offset origin The offset org is initialized by the ORG directive and is used by the DO and LO directives For more information refer to the individual descriptions of the DO LO and ORG directives Important The expressions associated with the REPT ds dz IF SPC COM DO and LO statements and the type lang attr rev and stack size PSECT directives must evaluate to constant values A relocatable result may change when linking or loading
76. ntical but the second command uses an alternative way of combining options r68 prog5 1l s c gt p r68 prog5 ls c gt p In this example the source program is read from the file prog5 The options and s are turned on and c is turned off Chapter 1 Basic Information About Assembler r68 Options Up to 10 options are allowed on the command line Each option is specified by a single letter preceded by a single hyphen or two hyphens Use a single hyphen to turn on an option and two hyphens to turn off an option Option Description a lt sym gt lt val gt Allows a symbol to be defined before the assembly begins The symbol is defined as if it appeared as the label on a set directive If a value is given the label is setto that value Otherwise the default value of 1 is assumed This option is most useful with the ifdef ifndef directives C Lists conditional assembly lines in an assembler listing By default this option is off d num Sets the number of lines per page for listing to num Default is 66 e Suppresses printing of errors Default off f Uses a form feed for page eject instead of line feeds Uses form feed for top of form Default off g Lists all generated code bytes Default off Writes a formatted assembler listing to standard output If not used only error messages are printed Default off m
77. o type and language fields in the module s psect directive The r68 and 168 programs are not compatible editions Be sure the correct programs are installed in the execution directory The relocatable module header in lt file gt was either not present or incorrectly formed All relocatable object headers start with the bytes DE AD FA CE Use the dump utility on the input file to verify this The most likely cause of this error is the wrong file was given on the command line This message is caused when the linker processes an old version of assembler output that contains more than 32k of code Re assembly of the source file will fix the problem This is an internal linker error Contact Microware if this error can be reproduced at will The output file for the module given by the o option cannot be created Possible causes are no access permissions or no disk space The symbol file for the module cannot be created Possible causes are no access permissions or no disk space One of the input files given could not be opened Possible causes are no access permissions non existent file or no free memory The z lt file gt could not be opened Possible causes are no access permissions non existent file or no free memory This is an internal linker error Contact Microware if this error can be reproduced at will Appendix B Assembler and Linker Error Codes Error Message Description duplicate symbol na
78. ock2 com 12 ends move l block2 8 a6 d0 File s2 a vsect block2 dC 11 2 3 ends 5 3 Chapter 5 Pseudo Instructions dc Define Constant Syntax label dc s expression lt expression gt The size extension s can be b for bytes W for words default for longwords Function dc generates sequences of one or more constants initialized data of various sizes within the program The argument s is a list of one or more expressions or character strings If more than one expression or string is used they are separated by commas A dc used in a vsect creates an initialized data variable read write in the process data area The initialization value is stored in a special section of the object code and is copied to the appropriate locations in the data area by the FSFORK system call A dc used outside a vsect is used to create read only constants in the program area The program should not change these constants Character string constants can be any sequence of printable ASCII characters enclosed in double quotes For dc w and dc l a string constant is padded with zeroes on the right end if it does not fill the final word or long word Therefore dc b is the most natural format for strings It is good practice to use an align directive after dc b directives to make sure the instruction counter is left on an even word boundary Examples dc b 1 20 A dc b index 2 1 0 0 1 dc w 1 10 100 1000 10000
79. of relative addresses assigned to symbols in the final object module The symbols are listed in numeric order This option is usually used with the m option S Sets the sticky bit in the module header causing the module to remain in the module directory even if the link count becomes zero W When used with s it displays symbols in alphabetic instead of numeric order Z Reads module names from standard input z file Reads module names from file The linker can generate raw code to run in non OS 9 environments The output is a pure binary file which is not in OS 9 memory module format The linker r option is used to create raw output files The hexadecimal address to place the modules in ROM is specified using the r option The address is used to make absolute references come out correctly Because it is assumed that the code will not be executed via the OS 9 fork system call which performs data area initialization no initialized data may be used for example dc in a vsect Your initialization code must set up the stack pointer a7 to point to a stack RAM area and the a6 register must point to the beginning of a global static RAM area vsect which should be initialized to zeros 6 7 Rules for Programming Techniques OS 9 Programming Techniques One of OS 9 s main features is its powerful memory management capabilities using software or software hardware methods This results in mu
80. of the monadic instructions is as follows Mnemonic Format lt ea gt FPn FPm FPn FPn lt monadic inst gt Chapter 1 Basic Information About Assembler The following 68881 floating point instructions use the above monadic syntax Mnemonic Description faos Absolute value facos Arc cosine fasin Arc sine fatan Arc tangent fatanh Hyperbolic arc tangent fcos Cosine fcosh Hyperbolic cosine fetox ex fetoxml e 1 fgetexp Get exponent fgetman Get mantissa fint nteger part fintrz nteger part round to zero flog10 L09g10 flog2 L0g flogn Loge flognp1 Loge i fneg egate fsin Sine fsinh Hyperbolic sine fsqrt Square root ftan Tangent ftanh Hyperbolic tangent ftentox 10 ftwotox 2x 1 23 Chapter 1 Basic Information About Assembler 1 24 Data Movement Instructions Mnemonic Format Syntax Description fmove X FPm FPn Floating move b w l s d X lt ea gt FPn b w l s d X FPm ea ea FPcr l FPcr lt ea gt fmovecr ccc F Pn Move from constant ROM fmovem lx flist ea lx ea flist X Dn lt ea gt X ea Dn Move multiple floating registers lt flist gt is a Sequence of floating registers Each register in the list is separated by a slash Consecutive registers may be grouped using a hyphen between the beginning and ending registers If form
81. only the symbols defining as yet undefined symbols are placed in the defined symbol table Symbol psects are used in the sys system library file to define system constants and offset values This procedure minimizes the amount of symbol table memory required for linking modules against the system library During the second phase the linker determines the size of the code data initialized data and remote memory areas The offsets of all code symbols are assigned based on each psect s position in the final module If the a option is used a symbol reference list is examined to determine if any code falls outside of the 16 bit offset addressing mode limit If any portion of the psect is farther than 32K from the destination an entry is reserved in the jumptable The offsets of all data symbols are assigned The uninitialized data memory is assigned first followed by the initialized data memory including the linker generated jumptable Finally the remote memory area is assigned The total size of the uninitialized and initialized data areas cannot exceed 64K The size of the remote memory area is limited only by the amount of contiguous free memory in the system The linker creates the output module during the third phase The module header for the appropriate module type is created and written to the output file Each input psect is re read from the appropriate input or library file The code and initialized data segments are read into an
82. r instruction mnemonic Whenever r68 encounters the name of a macro in the instruction field it outputs all the instructions given in the macro definition In effect macros allow you to create new machine language instructions For example suppose a program frequently must perform left shifts You can define this two instruction sequence as a macro For example dasl macro do a shift left asl l dl roxl 1 do endm The macro and endm directives specify the beginning and the end of the macro definition respectively The label of the macro directive specifies the name of the macro In this example the name is das When r68 encounters the dasl macro it can output code for asl and roxl Normally only the macro name is listed but you can use the x option of r68 to cause all instructions of the macro expansion to be listed Macros should not be confused with subroutines although they are similar A macro repetitively duplicates an in line code sequence every time it is used and allows some alteration of the instruction operands Subroutines appear exactly once and never change Subroutines are called using special instructions bsr jsr and rts In those cases where macros and subroutines can be used interchangeably macros usually produce longer but slightly faster programs Short macros 6 bytes or less are usually faster and shorter than subroutines because of the overhead of the needed bsr and rts instructions Macros can be an
83. r to the algebraic notation used in programming languages such as BASIC and FORTRAN Expressions consist of operands and operators Operands are symbolic names or constants Operators specify an arithmetic or logical function All assembler arithmetic uses long word internally 32 bit binary signed or unsigned integers in the range of 0 to 4294967295 for unsigned numbers or 2147483648 to 2147483647 for signed numbers In some cases expressions must result in a value which must fit in one byte for example 8 bit displacement in branch instructions Therefore they must be in the range of 0 to 255 for unsigned values and 128 to 127 for signed values If the result is outside of this range an error message will be returned Instructions that require a 16 bit value must result in a value within the range of 0 to 65535 unsigned or 32768 to 32767 signed Expressions are evaluated from left to right using the algebraic order of operations that is multiplications and divisions are performed before additions and subtractions Parentheses can be used to alter the natural order of evaluation Expression Operands The following items may be used as operands within an expression Decimal Numbers An optional minus sign followed by one to twelve digits For example 100 3164765 327167 999999 0 12 Hexadecimal Numbers A dollar sign or 0x followed by one to eight hexadecimal characters 0 9 AF or a f For example SEC
84. rea that contains the desired destination address leas are changed to move instructions that move the destination from a jump instruction in the jump table The linker automatically builds the required jump tables and includes them in the output file This allows large programs to overcome the 32K offset limit of bsr instructions without violating the OS 9 requirement for position independent code e qn Sets the module edition number n is used for the edition number in the final output module 1 is used if this option is not given g Outputs symbol modules for use by the user and or source debugger If the r files were created with the g option two symbol files are created one file name with stb appended the other with dbg appended If not compiled with the g option only the stb file is created If a directory named STB is present in the current execution directory the symbol files are placed there Otherwise they are placed in the current execution directory j Prints jump table calculation map See the description in the a option path Uses path as a library file A library file consists of one or more merged assembly ROF files Each psectin the file is checked to see if it resolves any unresolved references If so the module is included in the final output module otherwise it is skipped No mainline psects are allowed in a library file This option can be repeated up to 32 t
85. rences If the sub2 c psect were to appear before the sub1 c psect the symbol definition for sub2 would not be found Remember a psect appearing in a library file is retained for the final module only if the psect defines an as yet undefined symbol To examine this library relationship use the l option of rdump Chapter 6 The Linker Linker Defined and Linker The linker defines some symbols at link time that cannot be determined Recognized Symbols until the final code and data offsets are determined The linker defined symbols are Symbol Index register References _jmptbl a6 Offset to jumptable end a6 Last data offset assigned bname pcr Offset from the beginning of the module to module name btext pcr Offset from pc to beginning of the module The linker recognizes certain global labels as overrides to selected fields in the module header The linker places the value of these symbols into the appropriate field of the module header Symbol Definition _sysedit Edition number to place at M E dit _sysperm Permission value to place at M Accs _sysattr Attribute revision value to place at M Attr These symbols are typically set with the equ directive as _sysedit equ 21 sedition number _sysperm equ PRead_ Read module access permissions _sysattr equ ReEnt Ghost 8 revision module attributes The Linker Command Line The linker command line has the following syntax 168 options mainline
86. rof2 rofN options mainline is the pathlist of the mainline segment from which external references are resolved and a module header is generated A mainline module is indicated by non zero type lang value in the psect directive Names of additional ROFs rof2 through rofN used in the linkage process follow the mainline ROF pathlist No other ROF can contain a mainline psect The mainline and all subroutine files appear in the final linked object module whether actually referenced or not There is no limit to the number of ROFs that may be used Only 32 library files however may be specified AII 168 input files must be in relocatable object format ROF 6 5 Chapter 6 The Linker Psects that contain no data or code are handled by 168 in a special way This type of psect contains only symbols that define constants for example equ Only the symbols that define external references are placed in the linker s symbol table If used this type of psect is the last psect given and handles remaining unresolved references An example of this is the sys 1 file system definition library Linker Command Line Options The following options can appear on the command line options are case significant Option Description a Converts out of range bsrs and PC relative leas to jump table references bsrs that address labels over 32K distant are automatically converted to jsrs using a jump table in the initialized data a
87. ry size of a program s code or data However due to the characteristics of the 68000 architecture certain restrictions exist These depend on the addressing modes used Because of the software techniques OS 9 uses to provide a multi user and multi tasking environment user state programs cannot use either the absolute short or absolute long addressing modes for addressing code and data memory All references to the program code must use a PC relative addressing mode n pcr Relative with Offset n pcr Xn Relative with Index and Offset or any relative branch instructions All references to the program data must use a register indirect addressing mode An Register Indirect An Postincrement Register Indirect An Predecrement Register Indirect n An Register Indirect with Offset n An Xn Indexed Register Indirect with Offset The offsets of these addressing modes are 16 bit signed offsets This limits the usefulness of the offset to 32K Many non trivial programs rapidly exceed this 32K limit Because it is undesirable to require assembly language programmers and compilers to generate worst case code all the time the OS 9 assembler and linker provide facilities to access distant program and data addresses Chapter 7 05 9 Programming Techniques Data Area References OS 9 places the address of the data memory for a process in the A6 register The labels appearing in the program s vsects represent offsets When appli
88. s ending with a 68020 legal size specifier can cause ambiguities in the 68020 extended addressing modes For example to distinguish the label maxval l from the symbol maxval with the size attribute of long use maxval l The following examples are illegal symbol names This symbol name is illegal because 2move Starts with a digit Ibl 123 the pound sign is not a legal name character Names are defined when first used as a label on an instruction or directive statement They must be defined exactly one time in the program with the exception of set labels If a name is redefined that is used as a label more than once an error message is printed on subsequent definition s If a symbolic name is used in an expression and has not been defined the name is assumed to be external to the psect Information will be recorded about the reference so the linker can adjust the operand accordingly However external names cannot appear in operand expressions for assembler directives The assembler uses Motorola standard assembly language mnemonics and syntax For more specific information about individual instructions consult the following books M68000 16 32 Bit Microprocessor Programmer s Manual Prentice Hall Fourth Edition MC68020 32 Bit Microprocessor User s Manual Prentice Hall Second Edition MC68881 Floating Point Coprocessor User s Manual Prentice Hall First Edition The following register names are reserved and can
89. s page for error checking writ macro ifne 3 Must have exactly three arguments fail writ must have thr arguments endc ifgt L3 29 File name can be 1 29 chars fail writ File name too long endc moveq 1 d0 Get path path moveq 42 d1 Number of chars to write lea 3 a6 a0 Get address of buffer os9 ISWritLn endm Sometimes it is necessary to use labels within a macro If a macro containing a label is to be used more than once a method of generating unique label names is required to avoid multiple definition errors A backslash followed by an at sign appearing in a label in a macro expansion is replaced with a macro expansion serial number The macro expansion serial number is incremented each time the macro is expanded and is unique to that particular macro expansion Chapter 2 Macros Here is an example of a macro that uses unique labels test macro tst b stat a6 beq s t a addq 1 1 count a6 t a endm The macro expands as follows tst b stat a6 beq s t00001a addq 1 1 count a6 t00001a The second expansion is tst b stat a6 beq s t00002a addq 1 1 count a6 t00002a Important e simply expands to a number Proper syntax must be observed when constructing labels 2 5 Relocatable Program Sections Relocatable Program Sections A primary purpose of r68 is to permit programs to be composed of different segments that can be assembled separately Important To c
90. se of available memory RULE 3 All object code must be position independent OS 9 must be able to dynamically map a memory module to any block of physical addresses to allow a process to access more than one module at the same time It also allows memory management on systems that do not have memory management hardware with address relocation functions Writing position independent code involves using only PC relative addressing in branches and in accessing constant tables Absolute memory addresses should never be used in a program 7 1 Chapter 7 05 9 Programming Techniques Program and Data Memory References 7 2 RULE 4 All data storage must be position independent OS 9 assigns the address of the program s data area at the time the process is started by the F Fork system call Use of a position independent data area lets OS 9 run on systems with limited or nonexistent memory management hardware As with the object code module absolute addressing of variables is not permitted Instead OS 9 programs use the convention that register A6 is a pointer base address register to the program s data area and all addressing of variables use the 68000 indexed addressing modes The initialized and uninitialized data area are accessed by the Register Indirect with Offset addressing mode n An The remote data area is accessed by the Indexed Register Indirect with Offset addressing mode n An Xn OS 9 does not limit the memo
91. software in part or whole to any other party or on any other system may constitute copyright infringements and misappropriation of trade secrets and confidential processes which are the property of Microware and or other parties Unauthorized distribution of software may cause damages far in excess of the value of the copies involved For additional copies of this software and or documentation or if you have questions concerning the above notice the documentation and or software please contact your OS 9 supplier Microware and OS 9 are registered trademarks of Microware Systems Corporation Microware Systems Corporation e 1900 N W 114th Street Des Moines Iowa 50325 7077 Phone 515 224 1929 Preface Introduction The Microware 68000 Macro Assembler is a full feature relocating macro assembler and linker for OS 9 68000 systems It was designed for use with hand written or compiler generated programs This software is available as a resident assembler for use on OS 9 68000 systems as a cross compiler for OS 9 Level II based 6809 computers or as a cross compiler for any of the following systems VAX computer running UNIX BSD4 2 UNIX 4 3 or VMS 4 6 an Apollo computer running Domain 10 x a Sun Computer running SunOS 3 x a HP9000 computer running HP UX 6 3 a Delta Box computer running MV68 Some of the main features of the assembler linker package are support for OS 9 s modular multi tasking environment
92. t Each local reference has the following format Type Location flag 2 bytes Local Offset 4 bytes The type definition is determined by bit 0 of the first byte and bit 0 2 of the second byte pun unused setto 0 gt pese pp E Type Byte 1 Type Byte 2 The value of bit O of the first byte determines the interpretation of bit 0 2 of the second byte Chapter 3 Relocatable Program Sections unused set to 0 Location Byte 1 Type Byte 1 Type Byte 2 bit 0 bit 0 bit 1 bit 2 0 not common 0 data 0 not remote 0 uninitialized 1 initialized 1 remote 0 uninitialized 1 initialized 1 code or equ unused set to 0 not used 1 common unused set to 0 0 not remote unused set to 0 1 remote The location is determined by bit 1 of the first byte and bit 3 7 of the second byte k E L Location Byte 2 The value of bit 1 of the first byte determines the interpretation of bit 5 of the second byte Location Byte 1 Location Byte 2 bit5 0 data 1 code 0 not remote 1 remote unused set to 0 The other location bits of the second byte are interpreted as follows Bits 3 4 Size of Local Reference 01 1 byte 10 2 bytes 11 4 bytes Bit 6 Relative Reference If set this tells the linker that the reference is relative to the location o
93. t is specified it is relative to the current working data directory If the pathlist is enclosed in quotation marks the assembler searches for the file in the directory where the source file is located If the pathlist is enclosed in angle brackets gt the assembler searches for the file in dd defs on OS 9 systems or the appropriate directories for cross assemblers What Are Psuedo Instructions align Pseudo Instructions Pseudo instructions are special assembler statements that generate object code but do not correspond to actual 68000 machine instructions Their primary purpose is to create special sequences of code and or constant data to be included in the program Labels are optional on pseudo instructions Align to Even Byte Boundary Syntax align Function align aligns the next generated code or next assigned data offset on an even byte boundary in memory If the current value of the instruction counter is non even a zero byte is inserted in the object code The CPU program counter must always be word aligned for instructions If the align directive is specified in a vsect both the initialized and uninitialized location counters are aligned This statement is generally used after odd length constant tables character strings or character data are imbedded in the object code See Also The dc and ds descriptions 5 1 Chapter 5 Pseudo Instructions com 5 2 Reserve Memory for Common
94. t remote unused set to 0 1 remote The Object Code Section Object Code for the Module Variable Length The size of this section is found in the Size of Object Code bytes defined in the header section The Initialized Data Section Initialized Data Variable Length The size of this section is found in the Size of Initialized Data defined in the header section Chapter 3 Relocatable Program Sections Important You may omit the object code section and or the initialized data section If both are missing and the static data count is zero the module can only contain absolute equ symbols In this case the linker extracts only those symbols that resolve an external reference The OS 9 Sys l library module is an example It contains nothing but equ ed symbol definitions The Initialized Remote Data Section Initialized Remote Data Variable Length The size of this section is found in the Size of Remote Static storage bytes in the header section The Debug Information Section Debug Information Variable Length The size of this section is found in the Size of debug bytes in the header section External Reference Section External References Count 2 Bytes The count indicates the number of references to external symbols that follow External References Variable Each external reference has the following format Name 1 n bytes Reference Count 2 bytes References reference count x 6 bytes
95. t the time the program section is assembled The actual values of external references must be inserted later when the program is linked The linker can resolve a limited number of expressions involving external references These expressions can consist only of simple addition and subtraction operations involving two operands at most The following expression forms involving external references are supported All other forms are illegal External Absolute External Absolute External External The linker performs subtraction by negating one operand and then adding it to the other operand This method can cause problems on signed values of either word or byte length as the linker may report over underflow errors Therefore care should be taken to minimize the complexity of expressions involving external names Symbolic Names A symbolic name consists of up to 256 of the following characters Symbolic name Description alhanumers Taz AZ 0 9 underscore z at sign the dollar sign period The first character cannot be a digit dollar sign or a period The following are examples of legal symbol names HERE there SPL030 PGM A Q1020 1 t integer L 123 X a002 68000 Assembly Language Mnemonics Chapter 1 Basic Information About Assembler Important r68 does not match lowercase letters to uppercase letters The names val A and VAL A are considered different names Symbolic name
96. tatements may be used and may be nested within other if statements They cannot have labels There are several kinds of if statements each performing a different comparison Statement Description ifeq True if operand equals zero ifne True if operand does not equal zero iflt True if operand is less than zero ifle True if operand is less than or equal to zero ifgt True if operand is greater than zero ifge True if operand is greater than or equal to zero ifdef True only if the specified symbol is defined ifndef True only if the specified symbol is not defined The if statements that test for less than or greater than zero can test the relative value of two symbols if the symbols are subtracted in the operand expression For example the following statement is true if min is greater than max the statement literally means if max min 0 iflt max min The ifdef and ifndef directives are different from the other conditional assembly instructions in that their operand field is a single label rather than an expression For ifdef if the specified symbol has been defined the instructions within the conditional are assembled For ifndef if the symbol has not been defined the conditional is assembled A symbol is considered to be defined if it appears in the label field before the reference during the first pass ATTENTION Conditionals based on undefined but to be A defined values cause phasing
97. tension S is an optional scale factor If S is used it must be 1 2 4 or 8 Expression disp w An Definition Address Register Indirect with Offset disp s An Xn s S Address Register Indirect with Index Base Displacement Memory Indirect Post indexed disp s An Xn s S disp s disp s An Xn s S disp s Memory Indirect P re indexed For the memory indirect addressing modes all four parameters are optional The assembler encodes the proper modes to indicate the suppression of the missing parameters r68020 accepts the 68000 addressing modes d An and d An Xn s In this case the 68020 brief format extension format is generated If the operand begins with a left parenthesis the 68020 full format extension format is always generated Chapter 1 Basic Information About Assembler Example Extension length modes clr b var a6 Brief format clr b var a6 Full format with 32 bit displacement clr b var w a6 Full format with 16 bit displacement clr b var a6 d0 w 2 Full format with sized index register clr b var w a4 Memory Indirect Post indexed no outer disp clr b a4 Memory Indirect no inner or outer disp clr b d0 Memory Indirect no inner outer disp or index The following table contains the condition codes used with the assembler instructions described in this chapter Mnemonic Co
98. th the set directive Labels on set and equ statements are assigned the operand field value These statements allow any value to be associated with a symbolic name The assembler determines the type of a label from the instruction associated with that label If no instruction or directive is specified for a label in a vsect the label type is initialized data elsewhere the label type is that assigned to code Whenever possible however labels should be placed on the same line as the instruction or directive with which they are associated The Operation Field The operation field specifies the machine language instruction or assembler directive statement mnemonic name It immediately follows the label field It is separated from the prior field by one or more spaces x68 accepts instruction mnemonic names in either uppercase or lowercase characters Chapter 1 Basic Information About Assembler Instructions cause two or more bytes of object code to be generated depending on the specific instruction and addressing mode Some assembler directive statements such as dz and dc also cause object code to be generated Many 68000 instructions require a size attribute for example move b d0 d1 or move w d1 sp If no size attribute is specified a word w is assumed For example move d0 d1 is a word move Some instructions however have no choice of size attribute In this case no size attribute is allowed Operand Field
99. the data or instruction counters The Mainline Segment Each complete program must have one segment which is called the mainline segment It gives the linker the information necessary to create the OS 9 module header the module name the initial entry point etc A small program having only one segment will have only a mainline segment Programs created by linking two or more segments together will have a mainline segment followed by the other segments Whether or not a segment can be used as a mainline segment is determined by the typelang value appearing on the psect directive This is discussed in detail in the next section The Psect Directive Syntax psect name typelang attrev edition stacksize entrypt trapent Legal Psect Statements Any 68000 instruction mnemonic dc dz align vsect endsect os9 tcall ends ATTENTION as cannot be used within a psect 3 5 Chapter 3 Relocatable Program Sections The Vsect Directive 3 6 The psect is the program code section There can only be one psect per source file The psect directive initializes all assembler location counters and marks the start of the program segment All instruction statements and vsect data reservations must be declared within the psect endsect block The psect may have a parameter list containing a name followed by five or six expressions if the psect is to be a mainline segment or it can have no parameter list
100. y that a programmer would have to deal with the internals of an ROF The information given here is for informational purposes You can use the rdump program to extract this data from existing relocatable files There are eight sections to a relocatable object file the Header section the External Definitions section a the Object Code the Initialized Data the Remote Initialized Data the Debug Information a the External Reference section the Local Reference section The Header Section ROF Sync Bytes 4 Bytes Sync bytes used by 168 to recognize an ROF Type Language 2 Bytes The type language word from the psect The linker uses this to determine the desired OS 9 module format If this word is zero the routine is assumed to be a subroutine type module Only the mainline segment can have this word be non zero Attribute revision 2 Bytes Attribute revision word to place in the OS 9 module It is only meaningful on a mainline segment Assembly Valid 2 Bytes Word used to prevent the linker from linking erroneous modules It will be non zero if assembly errors have occurred Series 2 Bytes Tells the linker which assembler version was used This prevents problems that could occur in mixing different versions of the linker and assembler Date Time Assembled 6 Bytes Indicates the date and time of assembly Edition Number 2 Bytes OS 9 edition number to be placed in the output module for mainline segments

Allen-Bradley OS-9 Assembler-Linker

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