The architectural heart of the retro computer, proven on real chips. A Z80,
a 32K ROM, a 64K RAM and an inverter (address-decode glue) are wired
chip-to-chip over a shared address + data bus, no board:
ROM at 0x0000-0x7FFF rom.CE = A15
RAM at 0x8000-0xFFFF ram.CE = NOT A15 (the inverter chip)
RD -> both OE ; WR -> RAM WE
The ROM program writes 0x5A to RAM at 0x8000, clears A, reads it back, and
HALTs only if the byte survived. HALT going low proves the full core works:
the Z80 runs from ROM, the inverter decodes A15 to select RAM (the settle
kernel drives the combinational glue across hops), and the RAM latches a
write and returns it on a read over the shared tri-state bus, all within
synchronous bus cycles. Adds z80-ram-rom.c (boot image) + ram-64k/inverter
fixtures. 37 chipbus tests across 7 files pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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