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NES: MMC5 - Fixed edge cases in vertical split behavior 

Fixes 5200_update_while_in_frame test behavior (glitch pink scanline for values $91-$9F)
This commit is contained in:
Sour 2025-07-15 21:38:02 +09:00
parent a032574a05
commit c46bc68942
1 changed files with 14 additions and 7 deletions
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21
Core/NES/Mappers/Nintendo/MMC5.h
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@ -463,7 +463,6 @@ protected:
bool isNtFetch = addr >= 0x2000 && addr <= 0x2FFF && (addr & 0x3FF) < 0x3C0;
if(isNtFetch) {
//Nametable data, not an attribute fetch
_splitInSplitRegion = false;
_splitTileNumber++;
if(_ppuInFrame) {
@ -486,15 +485,23 @@ protected:
uint8_t column = (_splitTileNumber + 2) % 42;
if(addr >= 0x2000) {
if(isNtFetch) {
if(column <= 32 && ((_verticalSplitRightSide && column >= _verticalSplitDelimiterTile) || (!_verticalSplitRightSide && column < _verticalSplitDelimiterTile))) {
//Split region (for next 3 fetches, attribute + 2x tile data)
_splitInSplitRegion = true;
_splitTile = ((verticalSplitScroll & 0xF8) << 2) | column;
return _mapperRam[_splitTile];
} else {
if(column == 0) {
_splitInSplitRegion = !_verticalSplitRightSide;
}
if(column == _verticalSplitDelimiterTile && _splitTileNumber < 42) {
//Enter/exit split section when the current column matches the column number written to $5200
_splitInSplitRegion = !_splitInSplitRegion;
} else if(column > 32) {
//Outside of split region (or sprite data), result can get modified by ex ram mode code below
_splitInSplitRegion = false;
}
if(_splitInSplitRegion) {
//In vertical split region, override data received by the PPU
_splitTile = ((verticalSplitScroll & 0xF8) << 2) | column;
return _mapperRam[_splitTile];
}
} else if(_splitInSplitRegion) {
uint8_t shift = ((_splitTile >> 4) & 0x04) | (_splitTile & 0x02);
uint16_t atAddr = 0x3C0 | ((_splitTile & 0x380) >> 4) | ((_splitTile & 0x1F) >> 2);