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VRAM Write Loop

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Hey i’ve been working on my NES emulator and now i’m doing the PPU. I can display background of some games such as Donkey Kong, Popeye and NESTEST (although the colors are wrong) but in Mario and PAC-MAN the screen is just blank, I’ve logged all my VRAM writes and reads and from an emulator that is working. (ROM is pac-man)

In my emulator I’ve got this:
VRAM Write to: 180 with value 0
VRAM Write to: 162 with value 0
VRAM Write to: 724 with value 0
VRAM Write to: 706 with value 0
…. now those 4 just repeat infinitely

In the working emulator those four lines are present only once and then the log goes something like that:
VRAM Write to: 0 with value 45
VRAM Write to: 1 with value 45
….


I’ve been trying to debug it for quite a while now and I have no idea what is failing, My CPU passes NESTEST as well as BLARGG instruction tests (outside of few illegal opcodez that pac-man doesn’t use). I’ve been following this guide to get me started https://bugzmanov.github.io/nes_ebook/ but i’ve stared to change almost every PPU bit that i’ve written to copy the one from the guide and it still daoesnt work.

Statistics: Posted by Ziperix — Sun Jan 14, 2024 8:52 am — Replies 2 — Views 190



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