Assembler/Disassembler 101

[Peter Gargano]

Hopefully some strange characters resulting from cutting & pasting
have been removed in this version:
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Just a quick note on how to use a disassembler and/or assembler
specifically to work with GM BINs. Further information on ASHC11,
DHC11 and BINCVT is from:

 http://www.techedge.com.au/utils
 mailto:peter at techedge.com.au?subject=Assembler/Disassembler

Here's the overview: The following four commands can be used to
generate a disassembly of a BIN (AMXY.BIN), re-assemble that
disassembly (with a listing), convert the assembler's S19 output
to a binary file (AMXY.BIN), and compare the newly created file with
the original BIN file.

| C:\>dhc11 amxy -ov
| C:\>ashc11 amxy.dis -l
| C:\>bincvt amxy.s19 -o=amxy.new -ov
| C:\>fc amxy.bin amxy.new

More detail:

DHC11 takes a BIN file (say AMXY.BIN), and use the information
there, along with a control file, to generate output.  Here's
the control file's contents and the command to disassemble AMXY
as would be seen in a "DOS box":

| C:\>type amxy
| ;
| ;  AMXY Control file
|
| input  amxy.bin
| output amxy.DIS
|
| load $C000
|
| C:\>dhc11 amxy -ov
| DHC11 - 68HC11 Disassembler v1.2b (c) Copyright 2001 Tech Edge Pty. Ltd.
|
| Input file amxy.bin has 16384 bytes ($4000).
| Output file: amxy.DIS
| Code resides from $C000 to $FFFF ($4000 bytes).
| Load address: $C000
| No entry point - defaulting to disassembly from $D000 (ie. the vector @ $FFFE).
| Pass 1 found 138 new entry points.
| Pass 2 found 8 new entry points.
| Pass 3 found 0 new entry points.
| Total of 3 iteration(s) to find all code.

This produces the following "type" of output

|        fill    $00, 289
|        db      $FF, $FF, $00, $00, $00, $00, $00, $00, $00, $00
|        fill    $00, 2040
|;
|LD000   ldS     #$01FF
|        call    LD87B
|        ldaA    #$08
|        staA    L5000
|        ldX     #$0002

This can be immediately assembled (use ASCH11) to produce a list file
that looks like this

|                        244 ;
|d000 8e 01 ff           245 LD000   ldS     #$01FF
|d003 bd d8 7b           246         call    LD87B
|d006 86 08              247         ldaA    #$08
|d008 b7 50 00           248         staA    L5000

But if the DHC11 command was ...

| c:\>dhc11 amxy -ov a op

... then this forces address (the "a") and opcode (the "op") information
to be added to so the disassembly file looks like

|C6DD                            fill    $00, 289
|C7FE                            db      $FF, $FF, $00, $00, $00, $00, $00, $00
|C808                            fill    $00, 2040
|;
|D000    8E 01 FF        LD000   ldS     #$01FF
|D003    BD D8 7B                call    LD87B
|D006    86 08                   ldaA    #$08
|D008    B7 50 00                staA    L5000
|D00B    CE 00 02                ldX     #$0002
|D00E    FF 3F FC                stX     L3FFC

This is a "listing" type display direct from DHC11 and cannot
be re-assembled with ASHC11.

--------

If there's any list interest, I'll continue this series on

  "using my tools".

Other topics could include how to generate a better disassembly by
using the control file's many commands, and how to modify a disassembly
to add new code, etc.

Peter.
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