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VRC2: Added missing 1-bit latch at 6000-7FFF to fix Contra (J)

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This used to work because the game would be emulated with 8kb of work ram at 6000-7FFF, which had the same effect.  But the actual board does not have work ram, so it was removed when integrating the new NES 2.0 database
This commit is contained in:
Sour 2020-05-17 11:16:15 -04:00
parent 650dfb35f1
commit c52cacd9e5
1 changed files with 26 additions and 6 deletions
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32
Core/VRC2_4.h
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@ -32,7 +32,7 @@ class VRC2_4 : public BaseMapper
uint8_t _hiCHRRegs[8];
uint8_t _loCHRRegs[8];
bool _hasIRQ;
uint8_t _latch = 0;
void DetectVariant()
{
@ -78,18 +78,21 @@ class VRC2_4 : public BaseMapper
}
protected:
virtual uint16_t GetPRGPageSize() override { return 0x2000; }
virtual uint16_t GetCHRPageSize() override { return 0x0400; }
uint16_t GetPRGPageSize() override { return 0x2000; }
uint16_t GetCHRPageSize() override { return 0x0400; }
bool AllowRegisterRead() override { return true; }
void InitMapper() override
{
_irq.reset(new VrcIrq(_console));
DetectVariant();
_prgMode = GetPowerOnByte() & 0x01;
//PRG mode only exists for VRC4+ (so keep it as 0 at all times for VRC2)
_prgMode = _variant >= VRCVariant::VRC4a ? (GetPowerOnByte() & 0x01) : 0;
_prgReg0 = GetPowerOnByte() & 0x1F;
_prgReg1 = GetPowerOnByte() & 0x1F;
_hasIRQ = false;
_latch = false;
for(int i = 0; i < 8; i++) {
_loCHRRegs[i] = GetPowerOnByte() & 0x0F;
@ -97,6 +100,11 @@ class VRC2_4 : public BaseMapper
}
UpdateState();
RemoveRegisterRange(0, 0xFFFF, MemoryOperation::Read);
if(!_useHeuristics && _variant <= VRCVariant::VRC2c && _workRamSize == 0 && _saveRamSize == 0) {
AddRegisterRange(0x6000, 0x7FFF, MemoryOperation::Any);
}
}
void ProcessCpuClock() override
@ -131,8 +139,20 @@ class VRC2_4 : public BaseMapper
}
}
uint8_t ReadRegister(uint16_t addr) override
{
//Microwire interface ($6000-$6FFF) (VRC2 only)
return _latch | (_console->GetMemoryManager()->GetOpenBus() & 0xFE);
}
void WriteRegister(uint16_t addr, uint8_t value) override
{
if(addr < 0x8000) {
//Microwire interface ($6000-$6FFF) (VRC2 only)
_latch = value & 0x01;
return;
}
addr = TranslateAddress(addr) & 0xF00F;
if(addr >= 0x8000 && addr <= 0x8006) {
@ -291,6 +311,6 @@ class VRC2_4 : public BaseMapper
ArrayInfo<uint8_t> loChrRegs = { _loCHRRegs, 8 };
ArrayInfo<uint8_t> hiChrRegs = { _hiCHRRegs, 8 };
SnapshotInfo irq{ _irq.get() };
Stream(_prgReg0, _prgReg1, _prgMode, loChrRegs, hiChrRegs, _hasIRQ, irq);
Stream(_prgReg0, _prgReg1, _prgMode, loChrRegs, hiChrRegs, _latch, irq);
}
};