NES: Make OAM decay more obvious by displaying a diagonal line of spr…

…ites
SourMesen · Dec 3, 2023 · 08424ce · 08424ce
1 parent 6142ba3
commit 08424ce
Show file tree

Hide file tree

Showing 3 changed files with 17 additions and 30 deletions.
diff --git a/Core/Debugger/MemoryDumper.cpp b/Core/Debugger/MemoryDumper.cpp
@@ -231,13 +231,16 @@ void MemoryDumper::SetMemoryValue(MemoryType memoryType, uint32_t address, uint8
 				//TODOv2 find a cleaner way to implement this
 				//Prevent invalid memory values
 				switch(memoryType) {
-					case MemoryType::SnesCgRam: if(address & 0x01) value &= 0x7F; break;
-					case MemoryType::NesPaletteRam: value &= 0x3F; break;
-					case MemoryType::PcePaletteRam: if(address & 0x01) value &= 0x01; break;
+					case MemoryType::SnesCgRam: src[address] = (address & 0x01) ? (value & 0x7F) : value; break;
+					case MemoryType::NesSpriteRam: case MemoryType::NesSecondarySpriteRam: src[address] = (address & 0x03) == 0x02 ? (value & 0xE3) : value; break;
+					case MemoryType::NesPaletteRam: src[address] = value & 0x3F; break;
+					case MemoryType::PcePaletteRam: src[address] = (address & 0x01) ? (value & 0x01) : value; break;
+
+					default:
+						src[address] = value;
+						invalidateCache();
+						break;
 				}
-
-				src[address] = value;
-				invalidateCache();
 			}
 			break;
 	}

diff --git a/Core/NES/NesPpu.cpp b/Core/NES/NesPpu.cpp
@@ -1062,15 +1062,20 @@ template<class T> uint8_t NesPpu<T>::ReadSpriteRam(uint8_t addr)
 		uint64_t elapsedCycles = _console->GetCpu()->GetCycleCount() - _oamDecayCycles[addr >> 3];
 		if(elapsedCycles <= NesPpu<T>::OamDecayCycleCount) {
 			_oamDecayCycles[addr >> 3] = _console->GetCpu()->GetCycleCount();
-			return _spriteRam[addr];
 		} else {
 			if(_mask.SpritesEnabled) {
 				//When debugging with the break on decayed oam read flag turned on, break (only if sprite rendering is enabled to avoid false positives)
 				_emu->BreakIfDebugging(CpuType::Nes, BreakSource::NesBreakOnDecayedOamRead);
 			}
-			//If this 8-byte row hasn't been read/written to in over 3000 cpu cycles (~1.7ms), return 0x10 to simulate decay
-			return 0x10;
+
+			//If this 8-byte row hasn't been read/written to in over 3000 cpu cycles (~1.7ms),
+			//decay the row (set it to addr, clear the bits that don't exist on some bytes)
+			for(int i = 0; i < 8; i++) {
+				int sprAddr = (addr & 0xF8) | i;
+				_spriteRam[sprAddr] = (sprAddr & 0x03) == 0x02 ? (sprAddr & 0xE3) : sprAddr;
+			}
 		}
+		return _spriteRam[addr];
 	}
 }
 
@@ -1428,20 +1433,6 @@ template<class T> void NesPpu<T>::UpdateState()
 	}
 }
 
-template<class T> uint8_t* NesPpu<T>::GetSpriteRam()
-{
-	//Used by debugger
-	if(_enableOamDecay) {
-		for(int i = 0; i < 0x100; i++) {
-			//Apply OAM decay to sprite RAM before letting debugger access it
-			if((_console->GetCpu()->GetCycleCount() - _oamDecayCycles[i >> 3]) > NesPpu<T>::OamDecayCycleCount) {
-				_spriteRam[i] = 0x10;
-			}
-		}
-	}
-	return _spriteRam;
-}
-
 template<class T> uint32_t NesPpu<T>::GetPixelBrightness(uint8_t x, uint8_t y)
 {
 	//Used by Zapper, gives a rough approximation of the brightness level of the specific pixel

diff --git a/Core/NES/NesPpu.h b/Core/NES/NesPpu.h
@@ -127,13 +127,6 @@ class NesPpu : public BaseNesPpu
 	__forceinline void Exec();
 	void Run(uint64_t runTo) override;
 
-	uint8_t* GetSpriteRam();
-
-	uint8_t* GetSecondarySpriteRam()
-	{
-		return _secondarySpriteRam;
-	}
-
 	uint32_t GetPixelBrightness(uint8_t x, uint8_t y) override;
 
 	uint16_t GetPixel(uint8_t x, uint8_t y)