as86



as86(1)                                                                as86(1)




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

       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 assembler.

       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 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 even 486 or 586)

       -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 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
              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
              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  -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.



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 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.

              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 the third option is not strictly consistant but is in place
              mainly for asld compatibility.


                   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 correct but 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 trailing nul byte.

       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 definition

       Other 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 is expected to  run  on  (86,  186,  286,  386,  486,  586)
              instructions for cpus later than specified give a warning.

       USE32 [cpu]
              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)

       .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  force  the  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)  instructions which are shorthands for a short branch
              plus a long jump and ’BR’ which  is  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 BVS BR

       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 ORB OUTB 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 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
              RDMSR  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 WRMSR XADD XCHG XLAT XLATB XOR

       Floating point
              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



Using GASP

       The Gnu assembler preprocessor provides some reasonable implementations
       of 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  .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.


SEE ALSO

       as(1), ld86(1), bcc(1)


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 characters and
       the instruction to cpu checking is not included.

       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 ld86(1).




                                   Mar, 1999                           as86(1)

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