Z80 ram failure testing results in unexpected/missing leading errors

jwestfall69 / neogeo-diag-bios

Disassembly of smkdan's Neo Geo Diagnostics BIOS with added features

36 stars 8 forks source link

Closed jwestfall69 closed 4 years ago

jwestfall69 commented 4 years ago

Doing some failure testing with z80 ram

No ram chip results in YM2610 unexpected IRQ
WE disconnected results in YM2610 unexpected IRQ or RAM Data (00) errors
OE disconnected results in YM2610 I/O Error and a snow sound on speakers
CE disconnected results in generic Z80 Dead / Comm issue, expected c3, actual 03. 03 would have been the last command sent to the z80 for the slot switch, which is to reset.

jwestfall69 commented 4 years ago

b1fef6bd6897571534075441cc51d31b16e1c673 commit fixes up the erroneous YM2610 unexpected IRQ errors.

jwestfall69 commented 4 years ago

5ddc31df341a0f90fbda503bd84576ef0de26375 commit causes no/dead ram or OE stuck high to trigger a new dead output error.

Going to close this ticket and open separate ones for the different remaining z80 ram failures.