as86 - Assembler for 8086..80386 processors
as86 [-0123agjuw] [-lm[list]] [-n name] [-o obj] [-b[bin]] [-s sym] [-t textseg] src
as86_encap prog.s prog.v [prefix_] [as86 options]
as86 is an assembler for the 8086..80386 processors, it's syntax is closer to the
intel/microsoft form rather than the more normal generic form of the unix system
The src file can be '-' to assemble the standard input.
This assembler can be compiled to support the 6809 cpu and may even work.
as86_encap is a shell script to call as86 and convert the created binary into a C file
prog.v to be included in or linked with programs like boot block installers. The prefix_
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 include prefix_start prefix_size and
prefix_data to define and contain the code, plus integers containing the values of all
exported labels. Either or both the prog.s and prog.v arguments can be '-' for standard
-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 even 486 or
-a enable partial compatibility with Minix asld. This swaps the interpretation of
round brackets and square brackets as well as making alterations to the code
generation and syntax for 16bit jumps and calls. ("jmp @(bx)" is then a valid
-g only put global symbols in object or symbol file
-j replace all short jumps with similar 16 or 32 bit jumps, the 16 bit conditional
branches are encoded as a short conditional and a long unconditional branch.
-O this causes the assembler to add extra passes to try to use forward references to
reduce the bytes needed for some instructions. If the labels move on the last pass
the assembler will keep adding passes until 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 explicit br bmi bcc style opcodes for 8086 code or the jmp near style for
conditional i386 instructions and make sure all variables are defined before they
-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 -s option 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 encapsulation and related activities in relation
to binary files created with the -b option. If a binary file doesn't start at
location zero the first two items 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.
* 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 also
displayed 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 a segment and
offset. This means that the way this operator and the immediate prefix work are
like traditional assemblers.
Direct register addressing, the jump copies BX into PC.
Simple indirect register addressing, the jump moves the contents of the location
specified by BX into the PC.
Immediate value, ax becomes 1234.
Absolute addressing, ax is set to contents of location 1234. Note the third option
is not strictly consistant but is in place mainly for asld compatibility.
Indexed addressing, both formats are ok, I think the first is more correct but I
tend to used the second. :-)
IF, ELSE, ELSEIF, ENDIF
String compare (str1,str2)
Generate user error.
.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
Label type definition
EXPORT PUBLIC .DEFINE
Export label defined in this object
ENTRY Force linker to include the specified label in a.out
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)
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 string copied to output.
.ASCIZ Ascii string copied to output with trailing nul byte.
.BLKB RMB .SPACE
Space is counted in bytes.
Space is counted in words. (2 bytes each)
COMM .COMM LCOMM .LCOMM
Common area data definition
Other useful pseudo operations.
EQU Define label
SET Define re-definable label
Set assemble location
BLOCK Set assemble location and stack old one
ENDB Return to stacked assemble location
Insert new file (no quotes on name)
Define default operand size as 16 bit, argument is cpu type the code is expected to
run on (86, 186, 286, 386, 486, 586) instructions for cpus later than specified
give a warning.
Define default operand size as 32 bit, argument is cpu type the code is expected to
run on (86, 186, 286, 386, 486, 586) instructions for cpus later than specified
give a warning. If the cpu is not mentioned the assembler ensures it is >= 80386.
END End of compilation for this file.
.WARN Switch warnings
.LIST Listings on/off (1,-1)
Macro listings on/off (1,-1)
Macros, now working, the general form is like this.
IDENT Define object identity string.
SETDP Set DP value on 6809
MAP Set binary symbol table map number.
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 force the use of 80386 16bit
conditional branches. The 'Dword' and 'word' operators can control the size of
operands on far jumps and calls.
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) instructions which are
shorthands for a short branch plus a long jump and 'BR' which is the longest
unconditional jump (16 or 32 bit).
BCC BCS BEQ BGE BGT BHI BHIS BLE BLO BLOS BLT BMI BNE BPC BPL BPS BVC BVS BR
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 ORB OUTB
RCLB RCRB ROLB RORB SALB SARB SHLB SHRB SBBB SUBB TESTB XCHGB XORB
AAA AAD AAM AAS ADC ADD AND ARPL BOUND BSF BSR BSWAP BT BTC BTR BTS CALL CBW CDQ
CLC CLD CLI CLTS CMC CMP CMPS CMPSB CMPSD CMPSW CMPW CMPXCHG CSEG CWD CWDE DAA DAS
DEC DIV DSEG ENTER HLT IDIV IMUL IN INC INS INSB INSD INSW INT INTO INVD INVLPG INW
IRET IRETD J JA JAE JB JBE JC JCXE JCXZ JE JECXE JECXZ JG JGE JL JLE JMP JNA JNAE
JNB JNBE JNC JNE JNG JNGE JNL JNLE JNO JNP JNS JNZ JO JP JPE JPO JS JZ LAHF LAR LDS
LEA LEAVE LES LFS LGDT LGS LIDT LLDT LMSW LOCK LODB LODS LODSB LODSD LODSW LODW
LOOP LOOPE LOOPNE LOOPNZ LOOPZ LSL LSS LTR MOV MOVS MOVSB MOVSD MOVSW MOVSX MOVW
MOVZX MUL NEG NOP NOT OR OUT OUTS OUTSB OUTSD OUTSW OUTW POP POPA POPAD POPF POPFD
PUSH PUSHA PUSHAD PUSHF PUSHFD RCL RCR REP REPE REPNE REPNZ REPZ RET RETF RETI ROL
ROR SAHF SAL SAR SBB SCAB SCAS SCASB SCASD SCASW SCAW SEG SETA SETAE SETB SETBE
SETC SETE SETG SETGE SETL SETLE SETNA SETNAE SETNB SETNBE SETNC SETNE SETNG SETNGE
SETNL SETNLE SETNO SETNP SETNS SETNZ SETO SETP SETPE SETPO SETS SETZ SGDT SHL SHLD
SHR SHRD SIDT SLDT SMSW STC STD STI STOB STOS STOSB STOSD STOSW STOW STR SUB TEST
VERR VERW WAIT WBINVD XADD XCHG XLAT XLATB XOR
F2XM1 FABS FADD FADDP FBLD FBSTP FCHS FCLEX FCOM FCOMP FCOMPP FCOS FDECSTP FDISI
FDIV FDIVP FDIVR FDIVRP FENI FFREE FIADD FICOM FICOMP FIDIV FIDIVR FILD FIMUL
FINCSTP FINIT FIST FISTP FISUB FISUBR FLD FLD1 FLDL2E FLDL2T FLDCW FLDENV FLDLG2
FLDLN2 FLDPI FLDZ FMUL FMULP FNCLEX FNDISI FNENI FNINIT FNOP FNSAVE FNSTCW FNSTENV
FNSTSW FPATAN FPREM FPREM1 FPTAN FRNDINT FRSTOR FSAVE FSCALE FSETPM FSIN FSINCOS
FSQRT FST FSTCW FSTENV FSTP FSTSW FSUB FSUBP FSUBR FSUBRP FTST FUCOM FUCOMP FUCOMPP
FWAIT FXAM FXCH FXTRACT FYL2X FYL2XP1
The Gnu assembler preprocessor provides some reasonable implementations of user biased
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 .org commands, if you're not using
alternate syntax you can use org instead, otherwise use block and endb. The directive
export is translated into .global, which forces an import, if you are making a file using
-b use public or .define instead.
The GASP list options have no support in as86.
as(1), ld86(1), bcc(1)
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 characters and the instruction to cpu checking is not
The checking for instructions that work on specific cpus is probably not complete, the
distinction between 80186 and 80286 is especially problematic.
The .text and .data pseudo operators are not useful for raw binary files.
When using the org directive the assembler can generate object files that may break
Mar, 1999 as86(1)