genepensive wrote:
Video of the CHR errors:
http://sendvid.com/r67me113 - as you can see, it seems like it can read the first portion of the ROMs (notice how everything in the level select looks right), but maybe it can't switch banks properly? I'm not sure. There's not a lot of info on how to rewire MC-ACC boards.
So somehow it's selecting the wrong bank.
On the first screen:
* The boss selector is tiles in banks $7C-$7F, all tiles. Additionally sprites from bank $34 are used to fill in white-person-skin-tone bits. All display correctly.
* When Shadow Man is supposed to be striking a pose, his sprite tiles are supposed to be bank $2F, and the sprites are tile indices $F8 through $FB. Instead we see the smirk portion of a face, which comes from bank ... $3F.
On the next screen:
* All the background tiles are supposed to be from banks $5C-$5E, indices $0C-$0F at the top line; $1C-$1F and $2C-$2F in the middle; $3C-$3F above the platform, and instead we see the letters that are in bank ... $7C-$7E.
* Mega Man's sprites are in bank $00, and they display correctly.
In the first case, the A14 line is high when it shouldn't be; in the second case, the A15 line is high when it shouldn't be. And ... that's all I can tell. I don't know whether it's a wiring problem (although GameMachineJames implied it is) or a logic problem or whether the wiring problem is between the ROM and PPU, PPU and mapper, or CPU and mapper. But if I had to take a guess, I'd look closely for a short between CHR A14 and A15.
Quote:
edit: Just a thought.. perhaps CHR only needs to fill half of the EPROM, and the other half needs to be zero-filled? (Something about it being pulled "high" or "low"?)
I'm confident it's not that...