Atom

Atom is a single-pass Z80 assembler with an assembler core written in Z80. The native core fits in one 16 KiB bank and can assemble its own source. On a Mac, the atom command runs that core through the Debug80 runtime while a Node host handles files, conditional source, binary inputs and finished artifacts.

Install Atom

Atom is published as the public atom-z80 package and requires Node.js 20 or later:

npm install --global atom-z80

Create main.asm:

ORG 4000H

START:
    LD A,42
    HALT

Then assemble it:

atom --origin 4000H main.asm

The build appears under build/main.atom/current as binary, Intel HEX, NOBJ, listing, D8 source map and manifest files.

The language

Atom covers the complete Z80 instruction set claimed by its AZM oracle, including indexed, CB and ED forms. Its source language provides global and period-prefixed private labels, EQU, ORG, DB, DW, DS, ALIGN, INCBIN, character and string data, arithmetic expressions and LOW() and HIGH().

Host directives beginning with % select dependencies and conditional source. They are resolved before the native assembler reads the stream. Included files remain distinct source parts, so diagnostics and D8 mappings retain their original filenames and positions.

Read and use

• Atom Book 1 — Assembler Reference defines the command, source language and output formats.
• Atom Book 2 — Z80 Programming begins with registers and opcodes, then develops complete routines, algorithms and recursion.
• Atom Appendices contain the programming API and lookup tables for Atom and the Z80.
• Atom on npm provides the current package and version history.
• Atom source contains the Z80 core, host, engineering manual and correctness proofs.

Atom is licensed under GPL-3.0-only.