Categorygithub.com/retroenv/nesgocmdnesgodisasm
package
0.1.1
Repository: https://github.com/retroenv/nesgo.git
Documentation: pkg.go.dev
Overview
Dependencies
12
Dependents
0

# README

nesgodisasm - Disassembler for NES ROMs

nesgodisasm allows you to disassemble programs for the Nintendo Entertainment System (NES).

Features

  • Outputs ca65 compatible .asm files that can be used to reproduce the 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
  • Flexible architecture that allows it to create output modules for other assemblers

Check the issue tracker for planned features or known bugs.

Currently, only ROMs that use mapper 0 are supported.

Installation

There are different options to install nesgodisasm, the binary releases do not have any dependencies, compiling the tool from source code needs to have a recent version of Golang installed. To use the -verify option, cc65 needs to be installed.

  1. Download and unpack a binary release from Releases

  2. Install the latest release from source:

go install github.com/retroenv/nesgo/cmd/nesgodisasm@latest
  1. Build the current development version:
git clone https://github.com/retroenv/nesgo.git
cd nesgo
go build ./cmd/nesgodisasm
# use the dev version:
./nesgodisasm

Usage

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

Options

usage: nesgodisasm [options] <file to disassemble>

  -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