The public-domain Galaksija ROM (Voja Antonic; ROM A monitor + integer
BASIC, ROM B float BASIC, 8 KB) runs on a standalone Z80 + external ROM +
RAM + an inverter for address decode, all chip-to-chip over the shared bus,
no board:
ROM 0x0000-0x1FFF rom.CE = A13
RAM 0x2000-0x3FFF ram.CE = NOT A13 (the inverter chip)
RD -> both OE ; WR -> RAM WE
Pin-level boot proof (mirrors test_intel/test_z80/galaksija.test.js): watch
M1, read the address bus on each opcode fetch, and confirm the Z80 leaves
the reset vector (DI; SUB A; JP 0x03DA), reaches the init routine at 0x03DA,
and runs 1000+ fetches across 50+ distinct ROM addresses -- the real
firmware executing end-to-end through the settle-kernel bus. The on-screen
"READY" prompt is the next milestone (needs the video display chip
rendering the 0x2800 video RAM).
galaksija-rom.c embeds the public-domain ROM A+B image. 38 chipbus tests
across 8 files pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
David Montero Crespo