MAN page from Mandrake 10.X dev86-0.16.3-2mdk.i586.rpm

as86

Section: User Commands (1)
Updated: Mar, 1999
Index

NAME

as86 - Assembler for 8086..80386 processors

SYNOPSIS

as86[-0123agjuw][-lm[list]][-n name][-o obj][-b[bin]][-s sym][-t textseg]src

as86_encap prog.s prog.v[prefix_][as86 options]

DESCRIPTION

as86is an assembler for the 8086..80386 processors, it's syntax is closerto the intel/microsoft form rather than the more normal generic form ofthe unix system assembler.

Thesrcfile can be '-' to assemble the standard input.

This assembler can be compiled to support the 6809 cpu and may even work.

as86_encapis a shell script to call as86 and convert the created binary into a C fileprog.vto be included in or linked with programs like boot block installers.Theprefix_argument is a prefix to be added to all variables defined by the source,it defaults to the name of the source file. The variables defined includeprefix_startprefix_sizeandprefix_datato define and contain the code, plus integers containing the values of allexported labels.Either or both theprog.sandprog.varguments can be '-' for standard in/out.

OPTIONS

-0: start with 16-bit code segment, warn for all instructions > 8086
-1: start with 16-bit code segment, warn for all instructions > 80186
-2: start with 16-bit code segment, warn for all instructions > 80286
-3: start with 32-bit code segment, don't warn for any instructions. (not even486 or 586)
-a: enable partial compatibility with Minix asld. This swaps the interpretationof round brackets and square brackets as well as making alterations to thecode generation and syntax for 16bit jumps and calls. ("jmp @(bx)" is thena valid instruction)
-g: only put global symbols in object or symbol file
-j: replace all short jumps with similar 16 or 32 bit jumps, the 16 bitconditional branches are encoded as a short conditional and a longunconditional branch.
-O: this causes the assembler to add extra passes to try to use forwardreferences to reduce the bytes needed for some instructions. If the labels move on the last pass the assembler will keep adding passesuntil the labels all stabilise (to a maximum of 30 passes)It's probably not a good idea to use this with hand written assembler use the explicitbr bmi bccstyle opcodes for 8086 code or thejmp nearstyle for conditional i386 instructions and make sure all variables aredefined before they are used.
-l: produce list file, filename may follow
-m: print macro expansions in listing
-n: name of module follows (goes in object instead of source name)
-o: produce object file, filename follows
-b: produce a raw binary file, filename may follow.This is a 'raw' binary file with no header, if there's no-soption the file starts at location 0.
-s: produce an ASCII symbol file, filename follows.The format of this table is designed to be easy to parse for encapsulationand related activities in relation to binary files created with the-boption. If a binary file doesn't start at location zero the first twoitems in the table are the start and end addresses of the binary file.
-u: assume undefined symbols are imported-with-unspecified segment.
-w-: allow the assembler to print warning messages.
-t n: move all text segment data in segment n+3.

AS86 SOURCE

Special characters

*

Address of the start of the current line.

; !

Either of these marks the start of a comment. In addition any 'unexpected'character at the start of a line is assumed to be a comment (but it's alsodisplayed to the terminal).

$

Prefix for hexadecimal numbers, the 'C' syntax, eg 0x1234, is also accepted.

%

Prefix for binary numbers.

#

Prefix for immediate operands.

[ ]

Specifies an indirect operand.
Unlike MASM the assembler has no type information on labels just asegment and offset. This means that the way this operator and theimmediate prefix work are like traditional assemblers.

Examples:
mov ax,bx

jmp bx

Direct register addressing, the jump copies BX into PC.

        mov ax,[bx]        jmp [bx]

Simple indirect register addressing, the jump moves the contents of the location specified by BX into the PC.

mov ax,#1234

Immediate value, ax becomes 1234.

        mov ax,1234        mov ax,_hello        mov ax,[_hello]

Absolute addressing, ax is set to contents of location 1234. Note thethird option is not strictly consistant but is in place mainly for asldcompatibility.

        mov ax,_table[bx]        mov ax,_table[bx+si]        mov eax,_table[ebx*4]        mov ax,[bx+_table]        mov ax,[bx+si+_table]        mov eax,[ebx*4+_table]

Indexed addressing, both formats are ok, I think the first is more correctbut I tend to used the second. :-)
Conditionals

IF, ELSE, ELSEIF, ENDIF

Numeric condition

IFC, ELSEIFC

String compare (str1,str2)

FAIL .FAIL

Generate user error.Segment related

.TEXT .ROM .DATA .BSS

Set current segment. These can be preceded by the keyword.SECT

LOC

Set numeric segment 0=TEXT, 3=DATA,ROM,BSS, 14=MAX. The segment order set by the linker is now 0,4,5,6,7,8,9,A,B,C,D,E,1,2,3.Segment 0 and all segments above 3 are assumed to be text segment.Note the 64k size restrictions are not imposed for segments 3-14.Label type definition

EXPORT PUBLIC .DEFINE

Export label defined in this object

ENTRY

Force linker to include the specified label in a.out

.GLOBL .GLOBAL

Define label as external and force import even if it isn't used.

EXTRN EXTERN IMPORT .EXTERN

Import list of externally defined labels
NB: It doesn't make sense to use imports for raw binary files.

.ENTER

Mark entry for old binary file (obs)Data definition

DB .DATA1 .BYTE FCB

List of 1 byte objects.

DW .DATA2 .SHORT FDB .WORD

List of 2 byte objects.

DD .DATA4 .LONG

List of 4 byte objects.

.ASCII FCC

Ascii string copied to output.

.ASCIZ

Ascii string copied to output with trailingnulbyte.Space definition

.BLKB RMB .SPACE

Space is counted in bytes.

.BLKW .ZEROW

Space is counted in words. (2 bytes each)

COMM .COMM LCOMM .LCOMM

Common area data definitionOther useful pseudo operations.

.ALIGN .EVEN

Alignment

EQU

Define label

SET

Define re-definable label

ORG .ORG

Set assemble location

BLOCK

Set assemble location and stack old one

ENDB

Return to stacked assemble location

GET INCLUDE

Insert new file (no quotes on name)

USE16 [cpu]

Define default operand size as 16 bit, argument is cpu type the code isexpected to run on (86, 186, 286, 386, 486, 586) instructions for cpuslater than specified give a warning.

USE32 [cpu]

Define default operand size as 32 bit, argument is cpu type the code isexpected to run on (86, 186, 286, 386, 486, 586) instructions for cpuslater than specified give a warning. If the cpu is not mentioned theassembler ensures it is >= 80386.

END

End of compilation for this file.

.WARN

Switch warnings

.LIST

Listings on/off (1,-1)

.MACLIST

Macro listings on/off (1,-1)Macros, now working, the general form is like this.

    MACRO sax
       mov ax,#?1
    MEND
    sax(1)

Unimplemented/unused.

IDENT

Define object identity string.

SETDP

Set DP value on 6809

MAP

Set binary symbol table map number.

Registers

BP BX DI SI
EAX EBP EBX ECX EDI EDX ESI ESP
AX CX DX SP
AH AL BH BL CH CL DH DL
CS DS ES FS GS SS
CR0 CR2 CR3 DR0 DR1 DR2 DR3 DR6 DR7
TR3 TR4 TR5 TR6 TR7 ST

Operand type specifiers

BYTE DWORD FWORD FAR PTR PWORD QWORD TBYTE WORD NEAR

The 'near and 'far' do not allow multi-segment programming, all 'far'operations are specified explicitly through the use of the instructions:jmpi, jmpf, callf, retf, etc. The 'Near' operator can be used to forcethe use of 80386 16bit conditional branches. The 'Dword' and 'word' operators can control the size of operands on far jumps and calls.

General instructions.

These are in general the same as the instructions found in any 8086 assembler,the main exceptions being a few 'Bcc' (BCC, BNE, BGE, etc) instructionswhich are shorthands for a short branch plus a long jump and 'BR' whichis the longest unconditional jump (16 or 32 bit).

Long branches

BCC BCS BEQ BGE BGT BHI BHIS BLE BLO BLOS BLT BMI BNE BPC BPL BPS BVC BVSBR

Intersegment

CALLI CALLF JMPI JMPF

Segment modifier instructions

ESEG FSEG GSEG SSEG

Byte operation instructions

ADCB ADDB ANDB CMPB DECB DIVB IDIVB IMULB INB INCB MOVB MULB NEGB NOTB ORBOUTB RCLB RCRB ROLB RORB SALB SARB SHLB SHRB SBBB SUBB TESTB XCHGB XORB

Standard instructions

AAA AAD AAM AAS ADC ADD AND ARPL BOUND BSF BSR BSWAP BT BTC BTR BTS CALLCBW CDQ CLC CLD CLI CLTS CMC CMP CMPS CMPSB CMPSD CMPSW CMPW CMPXCHGCSEG CWD CWDE DAA DAS DEC DIV DSEG ENTER HLT IDIV IMUL IN INC INS INSBINSD INSW INT INTO INVD INVLPG INW IRET IRETD J JA JAE JB JBE JC JCXEJCXZ JE JECXE JECXZ JG JGE JL JLE JMP JNA JNAE JNB JNBE JNC JNE JNG JNGEJNL JNLE JNO JNP JNS JNZ JO JP JPE JPO JS JZ LAHF LAR LDS LEA LEAVE LESLFS LGDT LGS LIDT LLDT LMSW LOCK LODB LODS LODSB LODSD LODSW LODW LOOPLOOPE LOOPNE LOOPNZ LOOPZ LSL LSS LTR MOV MOVS MOVSB MOVSD MOVSW MOVSXMOVW MOVZX MUL NEG NOP NOT OR OUT OUTS OUTSB OUTSD OUTSW OUTW POP POPAPOPAD POPF POPFD PUSH PUSHA PUSHAD PUSHF PUSHFD RCL RCR REP REPE REPNEREPNZ REPZ RET RETF RETI ROL ROR SAHF SAL SAR SBB SCAB SCAS SCASB SCASDSCASW SCAW SEG SETA SETAE SETB SETBE SETC SETE SETG SETGE SETL SETLESETNA SETNAE SETNB SETNBE SETNC SETNE SETNG SETNGE SETNL SETNLE SETNOSETNP SETNS SETNZ SETO SETP SETPE SETPO SETS SETZ SGDT SHL SHLD SHR SHRDSIDT SLDT SMSW STC STD STI STOB STOS STOSB STOSD STOSW STOW STR SUB TESTVERR VERW WAIT WBINVD XADD XCHG XLAT XLATB XOR

Floating point

F2XM1 FABS FADD FADDP FBLD FBSTP FCHS FCLEX FCOM FCOMP FCOMPP FCOSFDECSTP FDISI FDIV FDIVP FDIVR FDIVRP FENI FFREE FIADD FICOM FICOMPFIDIV FIDIVR FILD FIMUL FINCSTP FINIT FIST FISTP FISUB FISUBR FLD FLD1FLDL2E FLDL2T FLDCW FLDENV FLDLG2 FLDLN2 FLDPI FLDZ FMUL FMULP FNCLEXFNDISI FNENI FNINIT FNOP FNSAVE FNSTCW FNSTENV FNSTSW FPATAN FPREMFPREM1 FPTAN FRNDINT FRSTOR FSAVE FSCALE FSETPM FSIN FSINCOS FSQRT FSTFSTCW FSTENV FSTP FSTSW FSUB FSUBP FSUBR FSUBRP FTST FUCOM FUCOMPFUCOMPP FWAIT FXAM FXCH FXTRACT FYL2X FYL2XP1

Using GASP

The Gnu assembler preprocessor provides some reasonable implementationsof user biased pseudo opcodes.

It can be invoked in a form similar to:

gasp: [-a...]file.s[file2.s]|
as86[...]-[-o obj] [-b bin]Be aware though that Gasp generates an error for .orgcommands, if you're not using alternate syntax you can use orginstead, otherwise use blockandendb.The directiveexportis translated into.global,which forces an import, if you are making a file using-busepublicor .defineinstead.
The GASP list options have no support in as86.

BUGS

The 6809 version does not support -0, -3, -a or -j.

If this assembler is compiled with BCC this is classed as a 'small'compiler, so there is a maximum input line length of 256 charactersand the instruction to cpu checking is not included.

The checking for instructions that work on specific cpus is probablynot complete, the distinction between 80186 and 80286 is especiallyproblematic.

The.textand.datapseudo operators are not useful for raw binary files.

When using theorgdirective the assembler can generate object files that may break ld86(1).

This document was created byman2html,using the manual pages.