#x65 Disassembler

Symbolic disassembler for 6502, 65C02 and 65816 (default).

This project was moved out of the x65 assembler project since it grew a little too large to be a code review tool. Apologies for the coding style which is rather brute force but re-assembling source is kind of a try and fail approach kind of thing.

Command Line Options

Typical command line ([*] = optional):

Usage

x65dsasm binary disasm.txt [$skip[-$end]] [addr=$xxxx] [cpu=6502/65C02/65816]
         [mx=0-3] [src] [prg] [data=$xx] [labels=labels.lbl]

• binary: file which contains some 65xx series instructions
• disasm.txt: output file (default is stdout)
• $skip-$end: first byte offset to disassemble to last byte offset to disassemble
• addr: disassemble as if loaded at addr (addr)
• data: this number of initial bytes in file is data and not code
• prg: file is a c64 program file starting with the load address
• cpu: set which cpu to disassemble for (default is 6502)
• src: export near assemblable source with guesstimated data blocks
• mx: set the mx flags which control accumulator and index register size
• labels: import labels from a file (each line: label=$xxxx [code]/[data] comment)
• graph: prefix the file with a calling graph
• graph+bra: include branches in the calling graph (increases size significantly)

Updates

• graph option exports a calling graph before the disassembly
• re-evaluation of separating segments after final cleanup
• c64kernal.lbl file defining c64 hw + kernal functions in the range of $e000-$fffa
• a78.lbl file defining Atari 7800 hardware addresses
• Switched the instruction info around to more easily determine read-only instructions
• Various improvements distinguishing between code and data
• c64.lbl file defining all c64 hardware addresses
• Tracking label references outside of the code including zero page
• Data / Code distinction improvements
• Local labels to improve code readability
• Improvements to code vs data determination
• Instrument labels through labels text file
• src option attempts to generate valid assembler source

Labels file format

Labels is a text file with one label declaration per line followed by the address to assign and the type of block to represent (code or data or pointers) followed by an optional comment. The labels file makes the most sense together with the src command line argument.

Addresses can define a range using a '-' after the address followed by an ending address. No automatic labels will be inserted within this range.

A special data format is pointers indicating a function pointer table, the label should be defined with a range to limit the size. Each pointer within the pointer table will be assigned a code label.

If the keyword "pointers" is followed by the word "data" the pointers will be interpreted as data pointers instead of code pointers.

A label can be redefined with a different name for read-only instructions by using the keyword read after the address. The label must first be defined as a data label to be assigned a read-only name. Read only instructions include ora, and, bit, eor, adc, sbc, lda, ldx, ldy, cmp, cpy and cpx.

Example labels file:

TIA_VSYNC = $00 data
TIA_CXM0P = $00 read
Init = $1000 code Entry point into code
SinTable = $1400 data 256 byte sinus table
Interrupt = $10f3 code Interrupt code
Callbacks = $1123-$112b pointers Array of function pointers
MapRefs = $1200-$1240 pointers data Array of data pointers
VIC_Sprite0_x = $d000 set sprite 0 x position
VIC_Sprite0_y = $d001 set sprite 0 y position
VIC_Sprite1_x = $d002 set sprite 1 x position
VIC_Sprite1_y = $d003 set sprite 1 y position

The simple way to work with a labels file is to copy an existing hardware file and add labels to it.

Sample output:

;
; FUNCTION CALLING GRAPH
;
; Code_140 ($d4af) [-]
;   Code_21 ($c5a3) [jmp]
;     Code_143 ($d56e) [jsr]
;       Code_109 ($cec3) [jsr]
;
; DISASSEMBLY
;
; Referenced from ResetVector + $0 (subroutine, $fffc)
; Referenced from IntVector + $0 (subroutine, $fffe)
Reset: ; $c000
  cld 
  sei 
; Referenced from Reset / .l_1 + $3 (branch, $c002)
.l_1: ; $c002

; -------------------------------- ;

; Referenced from Label_14 + $7 (subroutine)
; Referenced from Label_14 + $c (subroutine)
Label_11:
  lda $03,x
  bpl Label_13
; Referenced from Label_14 + $18 (subroutine)
Label_12:
  sec 
  lda #$00
  sbc $00,x
  sta $00,x
  lda #$00
  sbc $01,x
  sta $01,x
  lda #$00
  sbc $02,x
  sta $02,x
  lda #$00
  sbc $03,x
  sta $03,x
; Referenced from Label_11 + $2 (branch)
Label_13:
  rts 

; -------------------------------- ;

; Referenced from Label_1 + $1e (subroutine)
; Referenced from Label_16 + $1 (subroutine)
; Referenced from Label_24 + $b (subroutine)
; Referenced from Label_28 + $b (subroutine)
Label_14:
  lda $f7
  eor $f3

  lda #$e4
  jsr Label_16
  bne Label_27
  beq Label_27
; Referenced from Label_28 + $29 (branch)
Label_29:
  rts 

; -------------------------------- ;

; Referenced from Label_24 + $0 (data)
Label_30:
  dc.b $55, $55, $d5, $ff, $22, $22, $02, $00, $ff, $f2, $ff, $ff, $2e, $00, $00, $00