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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 "Debugger.h"
#include "NsfMapper.h"
#include "Console.h"
CPU::CPU(shared_ptr<Console> console)
{
_console = console;
_memoryManager = _console->GetMemoryManager();
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
};
typedef AddrMode M;
AddrMode addrMode[] = {
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
M::Imp, M::IndX, M::None, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Acc, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //0
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//1
M::Abs, M::IndX, M::None, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Acc, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //2
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//3
M::Imp, M::IndX, M::None, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Acc, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //4
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//5
M::Imp, M::IndX, M::None, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Acc, M::Imm, M::Ind, M::Abs, M::Abs, M::Abs, //6
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//7
M::Imm, M::IndX, M::Imm, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Imp, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //8
M::Rel, M::IndYW, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroY, M::ZeroY, M::Imp, M::AbsYW,M::Imp, M::AbsYW,M::AbsXW,M::AbsXW,M::AbsYW,M::AbsYW,//9
M::Imm, M::IndX, M::Imm, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Imp, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //A
M::Rel, M::IndY, M::None, M::IndY, M::ZeroX, M::ZeroX, M::ZeroY, M::ZeroY, M::Imp, M::AbsY, M::Imp, M::AbsY, M::AbsX, M::AbsX, M::AbsY, M::AbsY, //B
M::Imm, M::IndX, M::Imm, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Imp, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //C
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//D
M::Imm, M::IndX, M::Imm, M::IndX, M::Zero, M::Zero, M::Zero, M::Zero, M::Imp, M::Imm, M::Imp, M::Imm, M::Abs, M::Abs, M::Abs, M::Abs, //E
M::Rel, M::IndY, M::None, M::IndYW, M::ZeroX, M::ZeroX, M::ZeroX, M::ZeroX, M::Imp, M::AbsY, M::Imp, M::AbsYW,M::AbsX, M::AbsX, M::AbsXW,M::AbsXW,//F
};
memcpy(_opTable, opTable, sizeof(opTable));
memcpy(_addrMode, addrMode, sizeof(addrMode));
_instAddrMode = AddrMode::None;
_state = {};
_cycleCount = 0;
_operand = 0;
_spriteDmaCounter = 0;
_spriteDmaTransfer = false;
_dmcCounter = 0;
_dmcDmaRunning = false;
_cpuWrite = false;
_writeAddr = 0;
_irqMask = 0;
_state = {};
_prevRunIrq = false;
_runIrq = false;
}
void CPU::Reset(bool softReset, NesModel model)
{
_state.NMIFlag = false;
_state.IRQFlag = 0;
_cycleCount = -1;
_spriteDmaTransfer = false;
_spriteDmaCounter = 0;
_dmcCounter = -1;
_dmcDmaRunning = false;
_warnOnCrash = true;
//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;
_state.DebugPC = _state.PC;
_state.PreviousDebugPC = _state.PC;
if(softReset) {
SetFlags(PSFlags::Interrupt);
_state.SP -= 0x03;
} else {
_state.A = 0;
_state.SP = 0xFD;
_state.X = 0;
_state.Y = 0;
_state.PS = PSFlags::Interrupt;
_runIrq = false;
}
//The CPU takes some cycles before starting its execution after a reset/power up
for(int i = 0; i < (model == NesModel::NTSC ? 28 : 30); i++) {
_console->GetPpu()->Exec();
}
for(int i = 0; i < 10; i++) {
_console->GetApu()->ProcessCpuClock();
}
}
void CPU::Exec()
{
uint8_t opCode = GetOPCode();
_instAddrMode = _addrMode[opCode];
_operand = FetchOperand();
(this->*_opTable[opCode])();
if(_prevRunIrq) {
IRQ();
}
}
void CPU::IRQ()
{
#ifndef DUMMYCPU
uint16_t originalPc = PC();
#endif
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() | PSFlags::Reserved));
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::NMIVector));
_state.NMIFlag = false;
#ifndef DUMMYCPU
_console->DebugAddTrace("NMI");
_console->DebugProcessInterrupt(originalPc, _state.PC, true);
#endif
} else {
Push((uint8_t)(PS() | PSFlags::Reserved));
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::IRQVector));
#ifndef DUMMYCPU
_console->DebugAddTrace("IRQ");
_console->DebugProcessInterrupt(originalPc, _state.PC, false);
#endif
}
}
void CPU::BRK() {
Push((uint16_t)(PC() + 1));
uint8_t flags = PS() | PSFlags::Break | PSFlags::Reserved;
if(_state.NMIFlag) {
Push((uint8_t)flags);
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::NMIVector));
#ifndef DUMMYCPU
_console->DebugAddTrace("NMI");
#endif
} else {
Push((uint8_t)flags);
SetFlags(PSFlags::Interrupt);
SetPC(MemoryReadWord(CPU::IRQVector));
#ifndef DUMMYCPU
_console->DebugAddTrace("IRQ");
#endif
}
//Since we just set the flag to prevent interrupts, do not run one right away after this (fixes nmi_and_brk & nmi_and_irq tests)
_prevRunIrq = false;
}
void CPU::MemoryWrite(uint16_t addr, uint8_t value, MemoryOperationType operationType)
{
#ifdef DUMMYCPU
if(operationType == MemoryOperationType::Write || operationType == MemoryOperationType::DummyWrite) {
_writeAddresses[_writeCounter] = addr;
_isDummyWrite[_writeCounter] = operationType == MemoryOperationType::DummyWrite;
_writeValue[_writeCounter] = value;
_writeCounter++;
}
#else
_cpuWrite = true;;
_writeAddr = addr;
IncCycleCount();
while(_dmcDmaRunning) {
IncCycleCount();
}
_memoryManager->Write(addr, value, operationType);
//DMA DMC might have started after a write to $4015, stall CPU if needed
while(_dmcDmaRunning) {
IncCycleCount();
}
_cpuWrite = false;
#endif
}
uint8_t CPU::MemoryRead(uint16_t addr, MemoryOperationType operationType) {
#ifdef DUMMYCPU
uint8_t value = _memoryManager->DebugRead(addr);
if(operationType == MemoryOperationType::Read || operationType == MemoryOperationType::DummyRead) {
_readAddresses[_readCounter] = addr;
_readValue[_readCounter] = value;
_isDummyRead[_readCounter] = operationType == MemoryOperationType::DummyRead;
_readCounter++;
}
return value;
#else
IncCycleCount();
while(_dmcDmaRunning) {
//Stall CPU until we can process a DMC read
if((addr != 0x4016 && addr != 0x4017 && (_cycleCount & 0x01)) || _dmcCounter == 1) {
//While the CPU is stalled, reads are performed on the current address
//Reads are only performed every other cycle? This fixes "dma_2007_read" test
//This behavior causes the $4016/7 data corruption when a DMC is running.
//When reading $4016/7, only the last read counts (because this only occurs to low-to-high transitions, i.e once in this case)
_memoryManager->Read(addr);
}
IncCycleCount();
}
uint8_t value = _memoryManager->Read(addr, operationType);
return value;
#endif
}
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;
}
#if !defined(LIBRETRO) && !defined(DUMMYCPU)
if(_warnOnCrash && _console->GetSettings()->CheckFlag(EmulationFlags::DeveloperMode)) {
MessageManager::DisplayMessage("Error", "GameCrash", "Invalid OP code - CPU crashed.");
_warnOnCrash = false;
}
_console->BreakIfDebugging();
if(_console->IsNsf()) {
//Don't stop emulation on CPU crash when playing NSFs, reset cpu instead
_console->Reset(true);
return 0;
} else if(!_console->GetDebugger(false) && !_console->GetSettings()->CheckFlag(EmulationFlags::DeveloperMode)) {
//Throw an error and stop emulation core (if debugger is not enabled)
throw std::runtime_error("Invalid OP code - CPU crashed");
} else {
return 0;
}
#else
return 0;
#endif
}
void CPU::IncCycleCount()
{
_cycleCount++;
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;
#ifndef DUMMYCPU
_console->GetApu()->FillDmcReadBuffer();
_console->DebugAddTrace("DMC DMA End");
#endif
}
}
_console->ProcessCpuClock();
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 offsetValue)
{
_console->DebugAddTrace("Sprite DMA Start");
_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(_cycleCount % 2 != 0) {
DummyRead();
}
DummyRead();
_spriteDmaCounter = 256;
//DMA transfer starts at SpriteRamAddr and wraps around
for(int i = 0; i < 0x100; i++) {
//Read value
uint8_t readValue = 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")
MemoryWrite(0x2004, readValue);
_spriteDmaCounter--;
}
_spriteDmaTransfer = false;
_console->DebugAddTrace("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
_console->DebugAddTrace("DMC DMA Start");
_dmcDmaRunning = true;
if(_spriteDmaTransfer) {
if(_spriteDmaCounter == 2) {
_dmcCounter = 1;
} else if(_spriteDmaCounter == 1) {
_dmcCounter = 3;
} else {
_dmcCounter = 2;
}
} else {
if(_cpuWrite) {
if(_writeAddr == 0x4014) {
_dmcCounter = 2;
} else {
_dmcCounter = 3;
}
} else {
_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)
{
EmulationSettings* settings = _console->GetSettings();
uint32_t overclockRate = settings->GetOverclockRateSetting();
bool overclockAdjustApu = settings->GetOverclockAdjustApu();
uint32_t extraScanlinesBeforeNmi = settings->GetPpuExtraScanlinesBeforeNmi();
uint32_t extraScanlinesAfterNmi = settings->GetPpuExtraScanlinesAfterNmi();
uint32_t dipSwitches = _console->GetSettings()->GetDipSwitches();
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, dipSwitches);
if(!saving) {
settings->SetOverclockRate(overclockRate, overclockAdjustApu);
settings->SetPpuNmiConfig(extraScanlinesBeforeNmi, extraScanlinesAfterNmi);
settings->SetDipSwitches(dipSwitches);
}
}
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