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Fixed PPU memory mirroring issue - caused incorrect MMC3 IRQ timing in some games (i.e Burai Fighter)

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This commit is contained in:
Souryo 2014-07-26 22:14:08 -04:00
parent 35d2e9cc00
commit 674e64e655
2 changed files with 16 additions and 3 deletions
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17
Core/MemoryManager.cpp
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@ -121,9 +121,21 @@ uint16_t MemoryManager::ReadWord(uint16_t addr)
return lo | hi << 8;
}
uint8_t MemoryManager::ReadVRAM(uint16_t addr)
void MemoryManager::ProcessVRAMAccess(uint16_t &addr)
{
addr &= 0x3FFF;
if(addr >= 0x3000) {
//Need to mirror 0x3000 writes to 0x2000, this appears to be how hardware behaves
//Required for proper MMC3 IRQ timing in Burai Fighter
addr -= 0x1000;
}
_mapper->NotifyVRAMAddressChange(addr);
}
uint8_t MemoryManager::ReadVRAM(uint16_t addr)
{
ProcessVRAMAccess(addr);
if(addr <= 0x1FFF) {
return ReadMappedVRAM(addr & 0x1FFF);
} else {
@ -150,9 +162,8 @@ uint8_t MemoryManager::ReadVRAM(uint16_t addr)
void MemoryManager::WriteVRAM(uint16_t addr, uint8_t value)
{
_mapper->NotifyVRAMAddressChange(addr);
ProcessVRAMAccess(addr);
addr = addr & 0x3FFF;
if(addr <= 0x1FFF) {
WriteMappedVRAM(addr, value);
} else {

2
Core/MemoryManager.h
View file

@ -34,6 +34,8 @@ class MemoryManager: public Snapshotable
uint8_t ReadMappedVRAM(uint16_t addr);
void WriteMappedVRAM(uint16_t addr, uint8_t value);
void ProcessVRAMAccess(uint16_t &addr);
protected:
void StreamState(bool saving);