retroasm

An assembler for retro systems. It converts assembly source or an abstract syntax tree (AST) to machine code and ROM files.

Features

• 6502 assembly - Assembles source for NES output
• Library API - Assembles source text or an AST from Go programs
• Configuration files - Uses ca65-style files to define memory and segments
• Macros and conditionals - Processes macros and conditional assembly directives
• Expressions - Evaluates arithmetic and bitwise expressions in assembly source

Supported Systems

System	CPU	Status
NES	6502	Supported

Quick Start

Installation

Download a binary from Releases, or install from source with Go 1.25 or newer:

go install github.com/retroenv/retroasm/cmd/retroasm@latest

Basic Usage

Assemble a 6502 source file for NES. Use -o to set the output file:

retroasm -o game.nes program.asm

Use a ca65-style configuration file to set the memory layout:

retroasm -c memory.cfg -o game.nes program.asm

See the library guide for Go integration. Run retroasm -h to see all command options.