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CHIP-8 Disassembly Guide

This guide covers CHIP-8-specific features and usage of retrodisasm.

CHIP-8 Features

  • Execution Flow Tracing - Differentiates between code and data through program flow analysis
  • Complete Instruction Set - Handles all standard CHIP-8 instructions (35 opcodes)
  • retroasm Output - Generates retroasm compatible assembly

Usage

Basic Disassembly

Auto-detection from .ch8 or .rom extensions:

retrodisasm -o output.asm program.ch8
retrodisasm -o output.asm game.rom

Explicit system specification:

retrodisasm -s chip8 -o output.asm program.bin

Assembler

CHIP-8 disassembly only supports the retroasm format:

retrodisasm -a retroasm -o output.asm program.ch8

Binary Mode

Disassemble raw CHIP-8 binary:

retrodisasm -s chip8 -binary -base 0200 -o output.asm program.bin

CHIP-8 programs typically start at address 0x0200.

Batch Processing

Process multiple CHIP-8 ROMs:

retrodisasm -s chip8 -batch "*.ch8"
retrodisasm -s chip8 -batch "*.rom"

Output Customization

Remove Comments

Omit hex opcode bytes in comments:

retrodisasm -s chip8 -nohexcomments -o output.asm program.ch8

Omit file offsets in comments:

retrodisasm -s chip8 -nooffsets -o output.asm program.ch8

Reassembly

After disassembly, reassemble with retroasm:

retroasm output.asm -o output.ch8

CHIP-8 Instruction Set

retrodisasm supports all 35 standard CHIP-8 instructions:

  • Display: CLS, DRW
  • Flow: JP, CALL, RET, SE, SNE
  • Arithmetic: ADD, SUB, SUBN, OR, AND, XOR, SHR, SHL
  • Memory: LD (various addressing modes)
  • Random: RND
  • Timers: LD DT, LD ST
  • Keyboard: SKP, SKNP
  • BCD: LD B
  • Register operations: LD [I], LD F

Notes

  • CHIP-8 is a virtual machine architecture, not a physical system
  • The standard memory layout starts programs at address 0x0200
  • retrodisasm traces execution flow to identify code vs data
  • Verification (reassembly comparison) is not yet implemented for CHIP-8