Emulation/ANESE
1
0
Fork 0
mirror of https://github.com/daniel5151/ANESE.git synced 2025-04-02 10:32:00 -04:00
Code Issues Projects Releases Packages Wiki Activity
ANESE/research/personal_research/PPU_notes.md
Daniel Prilik ed2554fb65 move docs to research
2017-11-12 12:48:01 -08:00

739 B
Vendored
Raw Permalink Blame History

PPU Notes

  • Writes to the following registers are ignored if earlier than ~29658 CPU clocks after reset:
    • PPUCTRL
    • PPUMASK
    • PPUSCROLL
    • PPUADDR
    • This also means that the PPUSCROLL/PPUADDR latch will not toggle.
    • The other registers work immediately
  • If the NES is powered on after having been off for less than 20 seconds, register writes are ignored as if it were a reset, and register starting values differ:
    • PPUSTATUS = $80 (VBlank flag set)
    • OAMADDR = $2F or $01
    • PPUADDR = $0001
    • i'm probably not handling this case
  • The Reset button on the Control Deck resets the PPU only on the front-loading NES (NES-001). On top-loaders (Famicom, NES-101), the Reset button resets only the CPU.