asm8

A generic Intel 8080 assembler written in TypeScript. Runs with Bun.

Built primarily to assemble the Radio-86RK monitor ROM, but works with any Intel 8080 source.

Usage

Run directly from npm (no install required):

npx asm8080 <source.asm> [--split] [-o <dir>]
bunx asm8080 <source.asm> [--split] [-o <dir>]

Or with Bun from source:

bun run asm8.ts <source.asm> [--split] [-o <dir>]

• Default — produces a single 64 KB file 0000-FFFF.bin with sections placed at their addresses
• --split — produces one file per section, named SSSS-EEEE.bin (or name.bin if the section has a section directive)
• -o <dir> — write output files to the given directory (created if needed, default: current directory)

A section map is printed to stdout:

F800-FFFF  2048 bytes

Assembler features

• Two-pass assembly (forward references resolved automatically)
• Case-insensitive mnemonics, registers, and symbols
• All documented Intel 8080 instructions
• Directives: org, section, db, dw, equ, end
• Number formats: decimal (255), hex with h suffix (0FFh)
• Character literals: 'A' (usable anywhere a byte value is expected)
• Strings in db: db "hello" or db 'hello'
• Expressions with + and -: lxi h, base + offset - 1
• Named sections: section name after org names the section for --split output

Tests

bun test

• tests/asm8.test.ts — assembles monitor.asm and verifies byte-identical output against mon32.bin
• tests/asm8-instructions.test.ts — exercises all 8080 instruction encodings, directives, expressions, labels, and edge cases

Reference files

• target/monitor.asm — Radio-86RK monitor ROM source (1494 lines)
• target/mon32.bin — expected binary output (2048 bytes, F800-FFFF)