nesgodisasm allows you to disassemble programs for the Nintendo Entertainment System (NES).
- Outputs asm6*/ca65/nesasm compatible .asm files that can be used to reproduce the same original NES ROM
- Translates known RAM addresses to aliases
- Traces the program execution flow to differentiate between code and data
- Supports undocumented 6502 CPU opcodes
- Supports branching into opcode parts of an instruction
- Does not output trailing zero bytes of banks by default
- Batch processing mode to disassembling multiple ROMs at once
- Flexible architecture that allows it to create output modules for other assemblers
Support for mappers that use banking is currently experimental.
The tool uses a modern software stack that does not have any system dependencies beside requiring a somewhat modern operating system to run:
- Linux: 2.6.32+
- Windows: 10+
- macOS: 10.15 Catalina+
There are 2 options to install nesgodisasm:
- Download and unpack a binary release from Releases
or
- Compile the latest release from source:
go install github.com/retroenv/nesgodisasm@latest
Compiling the tool from source code needs to have a recent version of Golang installed.
To use the -verify option, the chosen assembler needs to be installed.
Disassemble a ROM:
nesgodisasm -o example.asm example.nes
The generated assembly file content will look like:
...
Reset:
sei ; $8000 78
cld ; $8001 D8
lda #$10 ; $8002 A9 10
sta PPU_CTRL ; $8004 8D 00 20
ldx #$FF ; $8007 A2 FF
txs ; $8009 9A
_label_800a:
lda PPU_STATUS ; $800A AD 02 20
bpl _label_800a ; $800D 10 FB
...
.segment "VECTORS"
.addr NMI, Reset, IRQ
Assemble an .asm file back to a ROM:
ca65 example.asm -o example.o
ld65 example.o -t nes -o example.nes
usage: nesgodisasm [options] <file to disassemble>
-a string
Assembler compatibility of the generated .asm file (asm6/ca65/nesasm) (default "ca65")
-batch string
process a batch of given path and file mask and automatically .asm file naming, for example *.nes
-binary
read input file as raw binary file without any header
-c string
Config file name to write output to for ca65 assembler
-cdl string
name of the .cdl Code/Data log file to load
-debug
enable debugging options for extended logging
-nohexcomments
do not output opcode bytes as hex values in comments
-nooffsets
do not output offsets in comments
-o string
name of the output .asm file, printed on console if no name given
-q perform operations quietly
-verify
verify the generated output by assembling with ca65 and check if it matches the input
-z output the trailing zero bytes of banks
* asm6f needs to be compiled manually from latest source to support all instructions, the release from 2018 does not support all instructions.
