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firmware/

p8xmon.asm — the P8X ROM monitor, the firmware that runs from the memory-card EEPROM at reset (origin $0000).

What it provides

  • Interactive monitor commands over the ACIA: E (examine/edit memory), D (dump, with paging — CR = next block, . = exit), I/F/B (CF init / format / boot), G (go), ?/H (help).
  • BIOS jump table at $0100 — a stable call interface (ABI) for P8X/OS and other programs: CONIN, CONOUT, CONST, CFINIT, CFREAD, CFWRITE, PUTS, PHEX8. Programs call fixed addresses here so they keep working even if the monitor internals move.

Build

Assembled by ../assembler/p8xasm.py into a 6 KB ROM image ($0000–$17FF; shrunk from 8 KB 2026-09-14) (the monitor + BIOS use ~4.3 KB; the rest is erased). The burnable image (and its Intel HEX) is built into ../rom/ by:

cd ../emulator && make rom        # -> rom/p8x-prog-rom.{bin,hex}

Reference