Atari Mega Archive 2/Atari Mega Archive CD - Volume 2.iso/8bit/language/a65.ntxt

Text File | 1995-04-22 | 53KB | 2,852 lines

23-Jun-89 23:50:44-PDT,7575;000000000000
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Date: 24 Jun 89 05:40:40 GMT
From: killer![e-mail]  (Charles Marslett)
Organization: The Unix(R) Connection, Dallas, Texas
Subject: An Atari Assembler: A65
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#    This is a shell archive (Part 2 of 3)
#
#    It contains the documentation (what little there is)
#    for the A65 (NON-macro) assembler.
#
#----cut here-----cut here-----cut here-----cut here----#
#!/bin/sh
# shar:   Shell Archiver
#    Run the following text with /bin/sh to create:
#    a65.doc
# This archive created: Fri Jun 23 20:31:09 1989
sed 's/^X//' << \SHAR_EOF > a65.doc
X
X
X                    A65 (A very simple 6502 assembler)
X
X                                   by
X                             Charles Marslett
X                             Wordmark Systems
X
X
XThe A65 assembler is modeled after the Atari MACRO Assembler (AMAC) that
Xwas distributed by APX along with the MEDIT editor and the DDT debugger.
XThe most significant thing about it is that the source files cannot contain
Xline numbers (so editors that use line numbers must be able to write an
Xunnumbered output file).  A second characteristic is that it is a disk-to-
Xdisk assembler (the source must be in a disk (or cassette) file and the
Xobject cannot be inserted directly into memory.
X
XThe assembler is run from the DOS menu using the 'L' command, and prompts
Xyou for the source file name, the object file name and the listing file
Xname:  a RETURN in response to the object and listing prompts will cause
Xthe assembler to generate files on the same drive with extensions '.OBJ'
Xand '.LST' using the same file name as the source file.  If no '.' appears
Xin the source file name, '.ASM' is its assumed extension.  A listing can
Xbe printed directly by specifying 'P:' as the list file or dumped to the
Xscreen by specifying 'E:'.  A '-' disables the listing if you do not want
Xone.
X
XA start at implementing support for the 65C02 opcodes is in the code, but
Xwhat is there has not been tested very thouroughly and most of the opcodes
Xand addressing modes are not in place yet.  Otherwise, the machine
Xinstructions are as any other standard 6502 assembler would expect.
XExpressions can include +, -, * and / operators as well as HIGH[] and LOW[]
Xfunctions to extract the high and low bytes of 16-bit numbers.  Brackets,
X[ and ], may be used to group terms in an expression if necessary.  Symbols
Xmay have up to 11 characters, including upper and lower case letters,
Xunderscores and numbers.  Symbols must start with an underscore or letter,
Xand case is significant except for the predefined assembler opcodes and the
Xregister names A, X and Y.
X
XThe machine opcodes recognized are:
X
X   ADC, AND, ASL, BCC, BCS, BEQ, BIT, BMI, BNE, BPL, BRA (65C02 only),
X   BRK, BVC, BVS, CLC, CLD, CLI, CLV, CMP, CPX, CPY, DEC, DEX, DEY,
X   EOR, INC, INX, INY, JMP, JSR, LDA, LDX, LDY, LSR, NOP, ORA, PHA,
X   PHP, PLA, PLP, ROL, ROR, RTI, RTS, SBC, SEC, SED, SEI, STA, STX,
X   STY, TAX, TAY, TSX, TXA, TXS, TYA
X
XThe assembler directives are:
X
XDB      defines a byte, in decimal (12), hex ($0C), octal (@14) or binary
X        (%00001100) and may also be a character string (enclosed in quotes)
XDC      defines a byte, as above, but with the high bit set (if defining a
X        string, only on the last byte of the string)
XDW      defines a word, low byte first, as if an indirect pointer
XDS      allocates a number of bytes without storing any data in them
X
XORG     sets the location counter to a fixed address
X*=      same as ORG
XEQU     defines a symbol to have a specific value
X=       same as EQU
X
X
X
X
X
X
X
X
XINCLUDE causes the file specified to be inserted at this point in the
X        assembly (can be nested if the DOS supports sufficient numbers
X        of files open at once -- the object, list and source files are
X        kept open at all times, and each level of nested includes requires
X        one more open file.  MYDOS and Atari DOS 2 allow 3 normally, which
X        does not allow a listing and include files.  If set to 5, the
X        assembler could generate a listing and handle 1 level of nested
X        includes)
XTITLE   specifies the first title line
XSUBTTL  allows entering a second title line
XPAGE    causes the assembler to go to the top of th next listing page
X
XEND     terminates the program and specifies INIT and RUN addresses
X
XLIST    a stub for future expansion
XMACRO   another stub (does nothing, not even generate an error)
XMEND    another stub
X
XOctal numbers, EQU, *=, and INIT and RUN addresses may have bugs in them --
Xgood luck.  Most of the rest has been debugged reasonably well.
X
XThe END statement can have the following forms:
X
X        END             no RUN or INIT vectors generated at all
X        END  ADDR       ADDR is the RUN entry point
X        END  ADDR,      ADDR is the INIT entry point (no RUN vector)
X        END  INIT,RUN   both vectors specified
X
X(This is what I call minimum documentation, I will add to it as questions
Xare asked)
X
X                        Charles Marslett
X                        8/21/85
X
X
X
XChanges since the first release:
X
XThe assembler now behaves more reasonably when a forward reference is
Xencountered (it used to just generate junque quietly!) -- forward references
Xare forced to 16-bit values if possible, otherwise A65 assumes you know what
Xyou are doing, and assumes it will be an 8-bit value when it is defined.
X
XThe assembler allows upper and lower case symbols, and it is case sensitive.
XIt still ignores case, however, when handling the directives and machine
Xopcodes as well as the register names ("A", "X" and "Y").  Underscores are
Xalso allow in symbols and are treated as letters (makes C people happy!).
XSymbols may also be up to 11 characters long (rather than 8 as before).
X
XThe initial load address is the HIMEM value from DOS (the lowest possible
Xload address) rather than a random value left over in memory.
X
XErrors are marked in the listing file (as before) but they are also echoed
Xto the screen, and the total number of errors (in HEX) are reported at the
Xend of the assembly.  If any errors occur, the automatic return to the DOS
Xprompt is delayed until the [RETURN] key is pressed to give you an opportunity
Xto note any (unexpected) errors reported.
X
X
X
X
X
X
X
X
X
XFinally, some errors that were previously accepted (and generated bad code)
Xare now caught and flagged as errors). These included multiply defined
Xsymbols and some invalid addressing modes.
X
X                        Charles Marslett
X                        6/16/89
SHAR_EOF
#    End of shell archive
exit 0
===========================================================================
Charles Marslett
STB Systems, Inc.  <== Apply all standard disclaimers
Wordmark Systems   <== No disclaimers required -- that's just me
[e-mail]
23-Jun-89 23:50:48-PDT,8139;000000000000
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Date: 24 Jun 89 05:42:26 GMT
From: killer![e-mail]  (Charles Marslett)
Organization: The Unix(R) Connection, Dallas, Texas
Subject: An Atari Assembler: A65
Message-Id: <[e-mail]>
Sender: [e-mail]
To: [e-mail]