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Mesen/Core/CPU.cpp

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#include "stdafx.h"
#include "CPU.h"
#include "PPU.h"
#include "APU.h"
#include "DeltaModulationChannel.h"
#include "TraceLogger.h"
#include "Debugger.h"
#include "NsfMapper.h"
CPU* CPU::Instance = nullptr;
CPU::CPU(MemoryManager *memoryManager) : _memoryManager(memoryManager)
{
CPU::Instance = this;
Func opTable[] = {
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
&CPU::BRK, &CPU::ORA, &CPU::HLT, &CPU::SLO, &CPU::NOP, &CPU::ORA, &CPU::ASL_Memory, &CPU::SLO, &CPU::PHP, &CPU::ORA, &CPU::ASL_Acc, &CPU::AAC, &CPU::NOP, &CPU::ORA, &CPU::ASL_Memory, &CPU::SLO, //0
&CPU::BPL, &CPU::ORA, &CPU::HLT, &CPU::SLO, &CPU::NOP, &CPU::ORA, &CPU::ASL_Memory, &CPU::SLO, &CPU::CLC, &CPU::ORA, &CPU::NOP, &CPU::SLO, &CPU::NOP, &CPU::ORA, &CPU::ASL_Memory, &CPU::SLO, //1
&CPU::JSR, &CPU::AND, &CPU::HLT, &CPU::RLA, &CPU::BIT, &CPU::AND, &CPU::ROL_Memory, &CPU::RLA, &CPU::PLP, &CPU::AND, &CPU::ROL_Acc, &CPU::AAC, &CPU::BIT, &CPU::AND, &CPU::ROL_Memory, &CPU::RLA, //2
&CPU::BMI, &CPU::AND, &CPU::HLT, &CPU::RLA, &CPU::NOP, &CPU::AND, &CPU::ROL_Memory, &CPU::RLA, &CPU::SEC, &CPU::AND, &CPU::NOP, &CPU::RLA, &CPU::NOP, &CPU::AND, &CPU::ROL_Memory, &CPU::RLA, //3
&CPU::RTI, &CPU::EOR, &CPU::HLT, &CPU::SRE, &CPU::NOP, &CPU::EOR, &CPU::LSR_Memory, &CPU::SRE, &CPU::PHA, &CPU::EOR, &CPU::LSR_Acc, &CPU::ASR, &CPU::JMP_Abs, &CPU::EOR, &CPU::LSR_Memory, &CPU::SRE, //4
&CPU::BVC, &CPU::EOR, &CPU::HLT, &CPU::SRE, &CPU::NOP, &CPU::EOR, &CPU::LSR_Memory, &CPU::SRE, &CPU::CLI, &CPU::EOR, &CPU::NOP, &CPU::SRE, &CPU::NOP, &CPU::EOR, &CPU::LSR_Memory, &CPU::SRE, //5
&CPU::RTS, &CPU::ADC, &CPU::HLT, &CPU::RRA, &CPU::NOP, &CPU::ADC, &CPU::ROR_Memory, &CPU::RRA, &CPU::PLA, &CPU::ADC, &CPU::ROR_Acc, &CPU::ARR, &CPU::JMP_Ind, &CPU::ADC, &CPU::ROR_Memory, &CPU::RRA, //6
&CPU::BVS, &CPU::ADC, &CPU::HLT, &CPU::RRA, &CPU::NOP, &CPU::ADC, &CPU::ROR_Memory, &CPU::RRA, &CPU::SEI, &CPU::ADC, &CPU::NOP, &CPU::RRA, &CPU::NOP, &CPU::ADC, &CPU::ROR_Memory, &CPU::RRA, //7
&CPU::NOP, &CPU::STA, &CPU::NOP, &CPU::SAX, &CPU::STY, &CPU::STA, &CPU::STX, &CPU::SAX, &CPU::DEY, &CPU::NOP, &CPU::TXA, &CPU::UNK, &CPU::STY, &CPU::STA, &CPU::STX, &CPU::SAX, //8
&CPU::BCC, &CPU::STA, &CPU::HLT, &CPU::AXA, &CPU::STY, &CPU::STA, &CPU::STX, &CPU::SAX, &CPU::TYA, &CPU::STA, &CPU::TXS, &CPU::TAS, &CPU::SYA, &CPU::STA, &CPU::SXA, &CPU::AXA, //9
&CPU::LDY, &CPU::LDA, &CPU::LDX, &CPU::LAX, &CPU::LDY, &CPU::LDA, &CPU::LDX, &CPU::LAX, &CPU::TAY, &CPU::LDA, &CPU::TAX, &CPU::ATX, &CPU::LDY, &CPU::LDA, &CPU::LDX, &CPU::LAX, //A
&CPU::BCS, &CPU::LDA, &CPU::HLT, &CPU::LAX, &CPU::LDY, &CPU::LDA, &CPU::LDX, &CPU::LAX, &CPU::CLV, &CPU::LDA, &CPU::TSX, &CPU::LAS, &CPU::LDY, &CPU::LDA, &CPU::LDX, &CPU::LAX, //B
&CPU::CPY, &CPU::CPA, &CPU::NOP, &CPU::DCP, &CPU::CPY, &CPU::CPA, &CPU::DEC, &CPU::DCP, &CPU::INY, &CPU::CPA, &CPU::DEX, &CPU::AXS, &CPU::CPY, &CPU::CPA, &CPU::DEC, &CPU::DCP, //C
&CPU::BNE, &CPU::CPA, &CPU::HLT, &CPU::DCP, &CPU::NOP, &CPU::CPA, &CPU::DEC, &CPU::DCP, &CPU::CLD, &CPU::CPA, &CPU::NOP, &CPU::DCP, &CPU::NOP, &CPU::CPA, &CPU::DEC, &CPU::DCP, //D
&CPU::CPX, &CPU::SBC, &CPU::NOP, &CPU::ISB, &CPU::CPX, &CPU::SBC, &CPU::INC, &CPU::ISB, &CPU::INX, &CPU::SBC, &CPU::NOP, &CPU::SBC, &CPU::CPX, &CPU::SBC, &CPU::INC, &CPU::ISB, //E
&CPU::BEQ, &CPU::SBC, &CPU::HLT, &CPU::ISB, &CPU::NOP, &CPU::SBC, &CPU::INC, &CPU::ISB, &CPU::SED, &CPU::SBC, &CPU::NOP, &CPU::ISB, &CPU::NOP, &CPU::SBC, &CPU::INC, &CPU::ISB //F
};
AddrMode addrMode[] = {
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
Imp, IndX, None, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //0
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //1
Abs, IndX, None, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //2
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //3
Imp, IndX, None, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //4
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //5
Imp, IndX, None, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //6
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //7
Imm, IndX, Imm, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //8
Rel, IndYW, None, IndYW, ZeroX, ZeroX, ZeroY, ZeroY, Imp, AbsYW, Imp, AbsYW, AbsXW, AbsXW, AbsYW, AbsYW, //9
Imm, IndX, Imm, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //A
Rel, IndY, None, IndY, ZeroX, ZeroX, ZeroY, ZeroY, Imp, AbsY, Imp, AbsY, AbsX, AbsX, AbsY, AbsY, //B
Imm, IndX, Imm, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //C
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //D
Imm, IndX, Imm, IndX, Zero, Zero, Zero, Zero, Imp, Imm, Imp, Imm, Abs, Abs, Abs, Abs, //E
Rel, IndY, None, IndYW, ZeroX, ZeroX, ZeroX, ZeroX, Imp, AbsY, Imp, AbsYW, AbsX, AbsX, AbsXW, AbsXW, //F
};
memcpy(_opTable, opTable, sizeof(opTable));
memcpy(_addrMode, addrMode, sizeof(addrMode));
}
void CPU::Reset(bool softReset)
{
_state.NMIFlag = false;
_state.IRQFlag = 0;
_cycleCount = -1;
_spriteDmaTransfer = false;
_spriteDmaCounter = 0;
_dmcCounter = -1;
_dmcDmaRunning = false;
//Used by NSF code to disable Frame Counter & DMC interrupts
_irqMask = 0xFF;
//Use _memoryManager->Read() directly to prevent clocking the PPU/APU when setting PC at reset
_state.PC = _memoryManager->Read(CPU::ResetVector) | _memoryManager->Read(CPU::ResetVector+1) << 8;
if(softReset) {
SetFlags(PSFlags::Interrupt);
_state.SP -= 0x03;
} else {
_state.A = 0;
_state.SP = 0xFD;
_state.X = 0;
_state.Y = 0;
_state.PS = PSFlags::Reserved | PSFlags::Interrupt;
_runIrq = false;
}
}
void CPU::Exec()
{
uint8_t opCode = GetOPCode();
_instAddrMode = _addrMode[opCode];
_operand = FetchOperand();
(this->*_opTable[opCode])();
if(_prevRunIrq) {
IRQ();
}
}
void CPU::IRQ()
{
uint16_t originalPc = PC();
DummyRead(); //fetch opcode (and discard it - $00 (BRK) is forced into the opcode register instead)
DummyRead(); //read next instruction byte (actually the same as above, since PC increment is suppressed. Also discarded.)
Push((uint16_t)(PC()));
if(_state.NMIFlag) {
Push((uint8_t)PS());
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::NMIVector));
_state.NMIFlag = false;
TraceLogger::LogStatic("NMI");
Debugger::ProcessInterrupt(originalPc, _state.PC, true);
} else {
Push((uint8_t)PS());
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::IRQVector));
TraceLogger::LogStatic("IRQ");
Debugger::ProcessInterrupt(originalPc, _state.PC, false);
}
}
uint16_t CPU::FetchOperand()
{
switch(_instAddrMode) {
case AddrMode::Acc:
case AddrMode::Imp: DummyRead(); return 0;
case AddrMode::Imm:
case AddrMode::Rel: return GetImmediate();
case AddrMode::Zero: return GetZeroAddr();
case AddrMode::ZeroX: return GetZeroXAddr();
case AddrMode::ZeroY: return GetZeroYAddr();
case AddrMode::Ind: return GetIndAddr();
case AddrMode::IndX: return GetIndXAddr();
case AddrMode::IndY: return GetIndYAddr(false);
case AddrMode::IndYW: return GetIndYAddr(true);
case AddrMode::Abs: return GetAbsAddr();
case AddrMode::AbsX: return GetAbsXAddr(false);
case AddrMode::AbsXW: return GetAbsXAddr(true);
case AddrMode::AbsY: return GetAbsYAddr(false);
case AddrMode::AbsYW: return GetAbsYAddr(true);
default: break;
}
Debugger::BreakIfDebugging();
if(NsfMapper::GetInstance()) {
//Don't stop emulation on CPU crash when playing NSFs, reset cpu instead
Reset(false);
return 0;
} else {
throw std::runtime_error("Invalid OP code - CPU crashed");
}
}
void CPU::IncCycleCount()
{
_cycleCount++;
_memoryManager->ProcessCpuClock();
if(_dmcDmaRunning) {
//CPU is being stalled by the DMC's DMA transfer
_dmcCounter--;
if(_dmcCounter == 0) {
//Update the DMC buffer when the stall period is completed
_dmcDmaRunning = false;
DeltaModulationChannel::SetReadBuffer();
TraceLogger::LogStatic("DMC DMA End");
}
}
PPU::ExecStatic();
APU::ExecStatic();
if(!_spriteDmaTransfer && !_dmcDmaRunning) {
//IRQ flags are ignored during Sprite DMA - fixes irq_and_dma
//"it's really the status of the interrupt lines at the end of the second-to-last cycle that matters."
//Keep the irq lines values from the previous cycle. The before-to-last cycle's values will be used
_prevRunIrq = _runIrq;
_runIrq = _state.NMIFlag || ((_state.IRQFlag & _irqMask) > 0 && !CheckFlag(PSFlags::Interrupt));
}
}
void CPU::RunDMATransfer(uint8_t* spriteRAM, uint8_t offsetValue)
{
TraceLogger::LogStatic("Sprite DMA Start");
Instance->_spriteDmaTransfer = true;
//"The CPU is suspended during the transfer, which will take 513 or 514 cycles after the $4014 write tick."
//"(1 dummy read cycle while waiting for writes to complete, +1 if on an odd CPU cycle, then 256 alternating read/write cycles.)"
if(Instance->_cycleCount % 2 != 0) {
Instance->DummyRead();
}
Instance->DummyRead();
Instance->_spriteDmaCounter = 256;
//DMA transfer starts at SpriteRamAddr and wraps around
for(int i = 0; i < 0x100; i++) {
//Read value
uint8_t readValue = Instance->MemoryRead(offsetValue * 0x100 + i);
//Write to sprite ram via $2004 ("DMA is implemented in the 2A03/7 chip and works by repeatedly writing to OAMDATA")
Instance->MemoryWrite(0x2004, readValue);
Instance->_spriteDmaCounter--;
}
Instance->_spriteDmaTransfer = false;
TraceLogger::LogStatic("Sprite DMA End");
}
void CPU::StartDmcTransfer()
{
//"DMC DMA adds 4 cycles normally, 2 if it lands on the $4014 write or during OAM DMA"
//3 cycles if it lands on the last write cycle of any instruction
TraceLogger::LogStatic("DMC DMA Start");
Instance->_dmcDmaRunning = true;
if(Instance->_spriteDmaTransfer) {
if(Instance->_spriteDmaCounter == 2) {
Instance->_dmcCounter = 1;
} else if(Instance->_spriteDmaCounter == 1) {
Instance->_dmcCounter = 3;
} else {
Instance->_dmcCounter = 2;
}
} else {
if(Instance->_cpuWrite) {
if(Instance->_writeAddr == 0x4014) {
Instance->_dmcCounter = 2;
} else {
Instance->_dmcCounter = 3;
}
} else {
Instance->_dmcCounter = 4;
}
}
}
uint32_t CPU::GetClockRate(NesModel model)
{
switch(model) {
default:
case NesModel::NTSC: return CPU::ClockRateNtsc; break;
case NesModel::PAL: return CPU::ClockRatePal; break;
case NesModel::Dendy: return CPU::ClockRateDendy; break;
}
}
void CPU::StreamState(bool saving)
{
uint32_t overclockRate = EmulationSettings::GetOverclockRateSetting();
bool overclockAdjustApu = EmulationSettings::GetOverclockAdjustApu();
uint32_t extraScanlinesBeforeNmi = EmulationSettings::GetPpuExtraScanlinesBeforeNmi();
uint32_t extraScanlinesAfterNmi = EmulationSettings::GetPpuExtraScanlinesAfterNmi();
Stream(_state.PC, _state.SP, _state.PS, _state.A, _state.X, _state.Y, _cycleCount, _state.NMIFlag,
_state.IRQFlag, _dmcCounter, _dmcDmaRunning, _spriteDmaCounter, _spriteDmaTransfer,
overclockRate, overclockAdjustApu, extraScanlinesBeforeNmi, extraScanlinesBeforeNmi);
if(!saving) {
EmulationSettings::SetOverclockRate(overclockRate, overclockAdjustApu);
EmulationSettings::SetPpuNmiConfig(extraScanlinesBeforeNmi, extraScanlinesAfterNmi);
}
}
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