Documentation for DISASM.PW4
----------------------------

DISASM.PW4 is a menu-file disassembler for the Model 100/102.  It disassembles
a file on the M100 menu (no need to load in running memory) and produces a
Custom Software compatible source (well, partly!).  Editing line 450 with T200
directory info should produce a 200 version.

1. Use

DISASM.PW4 produces an SRC file which is almost assembly ready.  Each line has
a label and all have tabs where needed.  But work will still be needed:

  1) Most disassemblers will not deal with assembler directives, instead
     trying to disassemble them into instructions.  This one is no exception.
     You really must study a listing with the HEX codes for this assessment;
     you can get such a listing with DISASM.PW2, which produces a "raw"
     disassembly (no tabs, labels, etc.).

  2) The labels need to be put into the operand column as appropriate.  Where
     a $XYZT matches an Lxyzt somewhere in the disassembly, you should (almost
     always!) replace the '$' with an 'L'.

  3) Excess labels can be removed to reduce the ASM size.  These most all
     labels not used in an operand after step (2).


2. Example

Following is a disassembly of DIRACC, with comments for constructing a source.
Note the (off-line!) use of a raw disassembly listing from DISASM.PW2 to find
messages and such.  And a menu version of DIRACC.CO  was created by 
modifying DIRACC.PW2 for the purpose of this exercise.  The following
listing is from DISASM.PW4, and contains tabs (unless you expanded 
them on download).


LF558#  POP     H       ;
LF559   CALL    $2C62
LF55C   CALL    $4231
LF55F   JMP     $5468   ;no labels to here
;***
LF562#  CALL    $F5AC   ;-->LF5AC
LF565   CALL    $6C7F
LF568   LXI     H,$0000
LF56B   SHLD    $F652   ;hi ram (not a label)
LF56E   JMP     $6C4F
;***
LF571#  CALL    $F5AC   ;-->LF5AC (again!)
LF574   CALL    $4222
LF577   LXI     H,$F587 ;-->LF587 (looks like it may be a msg, but isn't)
LF57A   SHLD    $F652   ;hi ram again
LF57D   LXI     H,$5E22
LF580   CALL    $5A7C
LF583   XRA     A
LF584   STA     $F650   ;another hi ram address
LF587#  CNZ     $4229
LF58A   CALL    $5D53
LF58D   LXI     H,$5E15
LF590   CALL    $27B1
LF593   CALL    $463E
LF596   RST     2
LF597   JZ      $F558   ;-->LF558
LF59A   CALL    $2206
LF59D   PUSH    H
LF59E   LXI     H,$0000
LF5A1   SHLD    $F6E7   ;hi ram address
LF5A4   MVI     A,$01
LF5A6   LXI     H,$F558 ;-->LF558 (could be msg label, but is not)
LF5A9   JMP     $5F71
;***
LF5AC#  CALL    $4231
LF5AF   LXI     H,$F5C3 ;-->LF5C3 (could be msg label -- and is!), because:
LF5B2   CALL    $27B1   ;print msg at HL until null (00)
LF5B5   MVI     L,$00
LF5B7   MVI     C,$C0
LF5B9   CALL    $5970
LF5BC   CALL    $4222
LF5BF   CALL    $7EAC
LF5C2   RET     
;***
LF5C3#  DCX     D       ;this is a message. Need hex code to get it
LF5C4   MOV     M,B;    ;it is ESC"E", followed by "DIRACC 100
LF5C5   MOV     B,H     ; Copyright 1985 Hugo Ferreyra
LF5C6   MOV     C,C     ;followed by ESC"F" -- one byte per line
LF5C7   MOV     D,D     ;in most cases.
LF5C8   MOV     B,C
LF5C9   MOV     B,E
LF5CA   MOV     B,E
LF5CB   RIM     
LF5CC   LXI     SP,$3030
LF5CF   RIM     
LF5D0   RIM     
LF5D1   MOV     B,E
LF5D2   MOV     L,A
LF5D3   MOV     M,B
LF5D4   MOV     A,C
LF5D5   MOV     M,D
LF5D6   MOV     L,C
LF5D7   MOV     H,A
LF5D8   MOV     L,B
LF5D9   MOV     M,H
LF5DA   RIM     
LF5DB   LXI     SP,$3839
LF5DE   DCR     M
LF5DF   RIM     
LF5E0   MOV     C,B
LF5E1   MOV     M,L
LF5E2   MOV     H,A
LF5E3   MOV     L,A
LF5E4   RIM     
LF5E5   MOV     B,M
LF5E6   MOV     H,L
LF5E7   MOV     M,D
LF5E8   MOV     M,D
LF5E9   MOV     H,L
LF5EA   MOV     A,C
LF5EB   MOV     M,D
LF5EC   MOV     H,C
LF5ED   DCX     D
LF5EE   MOV     M,C
LF5EF   NOP             ;this is 00h, and ends the print string.

Keep all leading labels (beginning of program and just after ';***'
lines as target points.  Keep the others identified above.  All
not marked by '#' can be deleted to save memory while assembling.

This is a bit oversimplified, but it gives the idea of using DISASM.PW4 &
DISASM.PW2 to recreate source files.


Phil Wheeler
71266,125
15 Nov 1987