Neogeo diag bios crosshatch testing / custom prog board

[ack]

1) With a modified z80 test cart the main bios screen now shows these codes (SM1, M1 S1) in the top right after z80 testing. Looks like they refer to the CHAR EPROMS, but what do they mean?

• M1 indicates that z80 tests were run, same as the original diag bios.
• S1 (Sn) is indicating a slot switch happened and which slot was switched to. This is mainly useful when testing multi-slot boards where you have a diag cart in each slot. You get confirmation about which slot was tested. The Sn will not show up on motherboards that don't have a build-in SM1 rom, since no slot switch happens.
• SM1 is indicating a crc32 check was done against the motherboard's SM1 rom and it was correct. The diag M1 rom will copy part of it self into ram, and switch execution to it. The diag sp1 is told to switch back to the SM1 rom, the ram running diag m1 code will do the crc32 check, then the diag sp1 is told to switch back to the diag m1 rom at which point execution jumps back to running from the diag m1 rom.

2) The p-rom test PROG board had three LED indicators on it (I relocated them on this version). Should all three of them be lit when the p-rom tests are running? And what does it mean if only some of them are lit?

SLOTCS LED indicates the slot is active. This should be on when you select the P-ROM test and I think just selecting the slot for z80 test should also cause it to be on. It should remain on unless you do something to switch to another slot. It might always be on for one slot boards, I dont recall.

When the P-ROM test is running the ROMOE and PORTADRS LEDs should be on, but likely a bit dim compared to the SLOTCS LED. They will be off when the test is not running.

There are 3 signals for reading from the P1 ROM on the cart. They are all on the cart edge

• ROMLOE (read lower byte only)
• ROMUOE (read upper byte only)
• ROMOE (read both)

The diag PROG cart is wired up to use ROMLOE and ROMUOE for reading from the SRAM chip. This leaves ROMOE untested and is why I have it wired to the LED so you can verify its getting enabled.

The same type of thing for the PORTADRS LED (usually for reading from P2 ROM / bank switching)

• PORTLOE (read lower byte only)
• PORTUOE (read upper byte only)
• PORTADRS (read both)