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Timing fixes - Sprite 0 hit flag and rendering disabled/enabled flag both needed to be delayed by 1 cycle. Fixes Micro Machines & Adventures of Dizzy.

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This commit is contained in:
Souryo 2016-01-11 17:18:01 -05:00
parent 3b73bb8f83
commit fc8add8262
2 changed files with 29 additions and 17 deletions
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42
Core/PPU.cpp
View file

@ -32,12 +32,13 @@ PPU::~PPU()
void PPU::Reset()
{
_sprite0HitCycle = -1;
_renderingEnabled = false;
_ignoreVramRead = 0;
_openBus = 0;
memset(_openBusDecayStamp, 0, sizeof(_openBusDecayStamp));
_skipTick = false;
_state = {};
_flags = {};
_statusFlags = {};
@ -272,7 +273,7 @@ void PPU::WritePaletteRAM(uint16_t addr, uint8_t value)
bool PPU::IsRenderingEnabled()
{
return _flags.BackgroundEnabled || _flags.SpritesEnabled;
return _renderingEnabled;
}
void PPU::SetControlRegister(uint8_t value)
@ -326,6 +327,11 @@ void PPU::SetMaskRegister(uint8_t value)
void PPU::UpdateStatusFlag()
{
if(_sprite0HitCycle >= 0 && _sprite0HitCycle < (int32_t)_cycle) {
_statusFlags.Sprite0Hit = true;
_sprite0HitCycle = -1;
}
_state.Status = ((uint8_t)_statusFlags.SpriteOverflow << 5) |
((uint8_t)_statusFlags.Sprite0Hit << 6) |
((uint8_t)_statusFlags.VerticalBlank << 7);
@ -526,12 +532,15 @@ uint32_t PPU::GetPixelColor(uint32_t &paletteOffset)
if(spriteColor != 0) {
//First sprite without a 00 color, use it.
if(i == 0 && backgroundColor != 0 && _sprite0Visible && _cycle != 256 && _flags.BackgroundEnabled) {
if(i == 0 && backgroundColor != 0 && _sprite0Visible && _cycle != 256 && _flags.BackgroundEnabled && !_statusFlags.Sprite0Hit && _sprite0HitCycle == -1) {
//"The hit condition is basically sprite zero is in range AND the first sprite output unit is outputting a non-zero pixel AND the background drawing unit is outputting a non-zero pixel."
//"Sprite zero hits do not register at x=255" (cycle 256)
//"... provided that background and sprite rendering are both enabled"
//"Should always miss when Y >= 239"
_statusFlags.Sprite0Hit = true;
//"Sprite zero hits act as if the image starts at cycle 2 (which is the same cycle that the shifters shift for the first time), so the sprite zero flag will be raised at this point at the earliest."
//Need to set the sprite 0 flag on the next PPU clock
_sprite0HitCycle = (int32_t)_cycle;
}
if(backgroundColor == 0 || !_spriteTiles[i].BackgroundPriority) {
@ -621,16 +630,11 @@ void PPU::ProcessPrerenderScanline()
//copy vertical scrolling value from t
_state.VideoRamAddr = (_state.VideoRamAddr & ~0x7BE0) | (_state.TmpVideoRamAddr & 0x7BE0);
}
} else if(_nesModel == NesModel::NTSC && _cycle == 338 && IsRenderingEnabled() && (_frameCount & 0x01)) {
//Check for the cycle skip in the else if block below
//If, at cycle 338 in the prerender scanline, rendering is enabled, we skip a tick (cycle 340) on the current frame
_skipTick = true;
} else if(_cycle == 339 && _skipTick) {
} else if(_nesModel == NesModel::NTSC && _cycle == 339 && IsRenderingEnabled() && (_frameCount & 0x01)) {
//This behavior is NTSC-specific - PAL frames are always the same number of cycles
//"With rendering enabled, each odd PPU frame is one PPU clock shorter than normal" (skip from 339 to 0, going over 340)
_cycle = -1;
_scanline = 0;
_skipTick = false;
} else if(_cycle >= 321 && _cycle <= 336) {
LoadTileInfo();
}
@ -641,16 +645,19 @@ void PPU::ProcessVisibleScanline()
if(_cycle > 0 && _cycle <= 256) {
LoadTileInfo();
DrawPixel();
ShiftTileRegisters();
if(IsRenderingEnabled()) {
CopyOAMData();
}
} else if(_cycle >= 321 && _cycle <= 336) {
LoadTileInfo();
} else if(_cycle == 340 && _sprite0HitCycle >= 0) {
//Set sprite 0 hit flag at the end of the scanline if the cycle count was set.
//This is just a way of not checking & setting the flag every cycle since the flag needs to be set with a 1 cycle delay
_statusFlags.Sprite0Hit = true;
_sprite0HitCycle = -1;
}
ProcessPreVBlankScanline();
@ -790,6 +797,9 @@ void PPU::Exec()
} else if(_scanline == _vblankEnd) {
EndVBlank();
}
//Rendering enabled flag is apparently set with a 1 cycle delay (i.e setting it at cycle 5 will render cycle 6 like cycle 5 and then take the new settings for cycle 7)
_renderingEnabled = _flags.BackgroundEnabled || _flags.SpritesEnabled;
}
void PPU::ExecStatic()
@ -878,6 +888,7 @@ void PPU::StreamState(bool saving)
Stream<uint8_t>(_oamCopybuffer);
Stream<bool>(_spriteInRange);
Stream<bool>(_sprite0Added);
Stream<int32_t>(_sprite0HitCycle);
Stream<uint8_t>(_spriteAddrH);
Stream<uint8_t>(_spriteAddrL);
Stream<bool>(_oamCopyDone);
@ -887,8 +898,7 @@ void PPU::StreamState(bool saving)
Stream<uint16_t>(_spriteDmaAddr);
Stream<uint16_t>(_spriteDmaCounter);
Stream<bool>(_skipTick);
Stream<bool>(_renderingEnabled);
Stream<uint8_t>(_openBus);
StreamArray<int32_t>(_openBusDecayStamp, 8);

4
Core/PPU.h
View file

@ -110,7 +110,6 @@ class PPU : public IMemoryHandler, public Snapshotable
NesModel _nesModel;
uint16_t _vblankEnd;
bool _skipTick;
PPUControlFlags _flags;
PPUStatusFlags _statusFlags;
@ -141,9 +140,12 @@ class PPU : public IMemoryHandler, public Snapshotable
uint8_t _oamCopybuffer;
bool _spriteInRange;
bool _sprite0Added;
int32_t _sprite0HitCycle;
uint8_t _spriteAddrH;
uint8_t _spriteAddrL;
bool _oamCopyDone;
bool _renderingEnabled;
void UpdateStatusFlag();