Me, Leandro, as a handdraw logo

ae6502

MOS 6502 assembler and emulator written in TypeScript

ae6502 is a toolkit for MOS 6502 processor emulation and development: a cycle-precise emulator and an assembler, living together in one TypeScript monorepo. An educational project, in the spirit of the community that keeps this 1975 CPU alive.

Features

  • Cycle-precise emulator with accurate instruction timing
  • Configurable memory mapping
  • Assembler for 6502 source
  • Test suite wired into GitHub Actions

Tech

  • TypeScript end to end
  • pnpm workspaces for the monorepo
  • GitHub Actions for CI

What I learned

  • Cycle accuracy on the 6502: page-boundary penalties and the cost of being exact.
  • Writing an assembler: tokenizing, addressing modes, and label resolution.
  • Structuring a TypeScript monorepo with shared tooling.

CC BY-NC-SA 4.0 2020–2026 © Leandro Peres. All rights reversed.