ABC80 Diagnostic ROM
ABC80 · VRAM · DRAM · SRAM
Memory diagnostic boot ROM for the Luxor ABC80 (March C RAM test). Requires lifting Z80 NMI.
A 4K boot ROM for the Luxor ABC80 that tests video RAM and system RAM. It is a port of the TRS-80 Diagnostic ROM by Dave Giller, Frank IZ8DWF, and Adrian Black (march RAM tests, stackless execution, beep codes).
It will not run correctly on an unmodified ABC80. Isolate Z80 pin 17 (/NMI) and pull it high through a resistor (about 4.7–10 kΩ to +5 V). NMI is driven by video VSYNC and is not maskable; this ROM uses SP as a threaded-code pointer, so an NMI destroys the test.
Program abc80diag.bin (or .hex) into a 2732 and fit it in the lowest 4K boot ROM socket (ROM0 / A5). Tests VRAM at $7C00, then loops DRAM/SRAM regions. Full procedure: the git README.
Monroe / OC8820 counterpart: Monroe Diagnostic ROM.