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