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2e29233b3b
EightBit/M6502/src/mos6502.cpp
Adrian Conlon 2e29233b3b Tidy up of the M6502 page fixup code
2024-03-01 23:18:24 +00:00

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#include "stdafx.h"
#include "../inc/mos6502.h"
EightBit::MOS6502::MOS6502(Bus& bus) noexcept
: LittleEndianProcessor(bus) {
RaisedPOWER.connect([this](EventArgs) {
X() = Bit7;
Y() = 0;
A() = 0;
P() = RF;
S() = Mask8;
lowerSYNC();
lowerRW();
});
}
DEFINE_PIN_LEVEL_CHANGERS(NMI, MOS6502)
DEFINE_PIN_LEVEL_CHANGERS(SO, MOS6502)
DEFINE_PIN_LEVEL_CHANGERS(SYNC, MOS6502)
DEFINE_PIN_LEVEL_CHANGERS(RDY, MOS6502)
DEFINE_PIN_LEVEL_CHANGERS(RW, MOS6502)
int EightBit::MOS6502::step() noexcept {
resetCycles();
ExecutingInstruction.fire(*this);
if (LIKELY(powered())) {
tick(); // A cycle is used, whether or RDY is high or not
if (UNLIKELY(lowered(SO())))
handleSO();
if (LIKELY(raised(RDY()))) {
lowerSYNC(); // Instruction fetch beginning
// Read the opcode within the existing cycle
assert(cycles() == 1 && "An extra cycle has occurred");
// Can't use fetchByte, since that would add an extra tick.
raiseRW();
opcode() = BUS().read(PC()++);
assert(cycles() == 1 && "BUS read has introduced stray cycles");
// Priority: RESET > NMI > INT
if (UNLIKELY(lowered(RESET())))
handleRESET();
else if (UNLIKELY(lowered(NMI())))
handleNMI();
else if (UNLIKELY(lowered(INT()) && !interruptMasked()))
handleINT();
// Whatever opcode is available, execute it.
execute();
}
}
ExecutedInstruction.fire(*this);
return cycles();
}
// Interrupt (etc.) handlers
void EightBit::MOS6502::handleSO() noexcept {
raiseSO();
P() |= VF;
}
void EightBit::MOS6502::handleRESET() noexcept {
raiseRESET();
m_handlingRESET = true;
opcode() = 0x00; // BRK
}
void EightBit::MOS6502::handleNMI() noexcept {
raiseNMI();
m_handlingNMI = true;
opcode() = 0x00; // BRK
}
void EightBit::MOS6502::handleINT() noexcept {
raiseINT();
m_handlingINT = true;
opcode() = 0x00; // BRK
}
void EightBit::MOS6502::interrupt() noexcept {
const bool reset = m_handlingRESET;
const bool nmi = m_handlingNMI;
if (reset) {
dummyPush(PC().high);
dummyPush(PC().low);
dummyPush(P());
} else {
const bool irq = m_handlingINT;
const bool hardware = nmi || irq || reset;
const bool software = !hardware;
pushWord(PC());
push(P() | (software ? BF : 0));
}
set_flag(IF); // Disable IRQ
const uint8_t vector = reset ? RSTvector : (nmi ? NMIvector : IRQvector);
BUS().ADDRESS() = { vector, 0xff };
jump(getWordPaged());
m_handlingRESET = m_handlingNMI = m_handlingINT = false;
}
//
void EightBit::MOS6502::busWrite() noexcept {
tick();
lowerRW();
Processor::busWrite();
}
uint8_t EightBit::MOS6502::busRead() noexcept {
tick();
raiseRW();
return Processor::busRead();
}
//
int EightBit::MOS6502::execute() noexcept {
raiseSYNC(); // Instruction fetch has now completed
switch (opcode()) {
case 0x00: swallow_fetch(); interrupt(); break; // BRK (implied)
case 0x01: A() = orr(A(), AM_IndexedIndirectX()); break; // ORA (indexed indirect X)
case 0x02: jam(); break; // *JAM
case 0x03: slo(AM_IndexedIndirectX()); break; // *SLO (indexed indirect X)
case 0x04: AM_ZeroPage(); break; // *NOP (zero page)
case 0x05: A() = orr(A(), AM_ZeroPage()); break; // ORA (zero page)
case 0x06: memoryReadModifyWrite(asl(AM_ZeroPage())); break; // ASL (zero page)
case 0x07: slo(AM_ZeroPage()); break; // *SLO (zero page)
case 0x08: swallow(); php(); break; // PHP (implied)
case 0x09: A() = orr(A(), AM_Immediate()); break; // ORA (immediate)
case 0x0a: swallow(); A() = asl(A()); break; // ASL A (implied)
case 0x0b: anc(AM_Immediate()); break; // *ANC (immediate)
case 0x0c: { auto ignored = Address_Absolute(); } break; // *NOP (absolute)
case 0x0d: A() = orr(A(), AM_Absolute()); break; // ORA (absolute)
case 0x0e: memoryReadModifyWrite(asl(AM_Absolute())); break; // ASL (absolute)
case 0x0f: slo(AM_Absolute()); break; // *SLO (absolute)
case 0x10: branch(negative() == 0); break; // BPL (relative)
case 0x11: A() = orr(A(), AM_IndirectIndexedY()); break; // ORA (indirect indexed Y)
case 0x12: jam(); break; // *JAM
case 0x13: slo_IndirectIndexedY(); break; // *SLO (indirect indexed Y)
case 0x14: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0x15: A() = orr(A(), AM_ZeroPageX()); break; // ORA (zero page, X)
case 0x16: memoryReadModifyWrite(asl(AM_ZeroPageX())); break; // ASL (zero page, X)
case 0x17: slo(AM_ZeroPageX()); break; // *SLO (zero page, X)
case 0x18: swallow(); reset_flag(CF); break; // CLC (implied)
case 0x19: A() = orr(A(), AM_AbsoluteY()); break; // ORA (absolute, Y)
case 0x1a: swallow(); break; // *NOP (implied)
case 0x1b: slo_AbsoluteY(); break; // *SLO (absolute, Y)
case 0x1c: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0x1d: A() = orr(A(), AM_AbsoluteX()); break; // ORA (absolute, X)
case 0x1e: memoryReadModifyWrite(asl(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // ASL (absolute, X)
case 0x1f: slo_AbsoluteX(); break; // *SLO (absolute, X)
case 0x20: jsr(); break; // JSR (absolute)
case 0x21: A() = andr(A(), AM_IndexedIndirectX()); break; // AND (indexed indirect X)
case 0x22: jam(); break; // *JAM
case 0x23: rla(AM_IndexedIndirectX()); break; // *RLA (indexed indirect X)
case 0x24: bit(A(), AM_ZeroPage()); break; // BIT (zero page)
case 0x25: A() = andr(A(), AM_ZeroPage()); break; // AND (zero page)
case 0x26: memoryReadModifyWrite(rol(AM_ZeroPage())); break; // ROL (zero page)
case 0x27: rla(AM_ZeroPage()); break; // *RLA (zero page)
case 0x28: swallow(); plp(); break; // PLP (implied)
case 0x29: A() = andr(A(), AM_Immediate()); break; // AND (immediate)
case 0x2a: swallow(); A() = rol(A()); break; // ROL A (implied)
case 0x2b: anc(AM_Immediate()); break; // *ANC (immediate)
case 0x2c: bit(A(), AM_Absolute()); break; // BIT (absolute)
case 0x2d: A() = andr(A(), AM_Absolute()); break; // AND (absolute)
case 0x2e: memoryReadModifyWrite(rol(AM_Absolute())); break; // ROL (absolute)
case 0x2f: rla(AM_Absolute()); break; // *RLA (absolute)
case 0x30: branch(negative()); break; // BMI (relative)
case 0x31: A() = andr(A(), AM_IndirectIndexedY()); break; // AND (indirect indexed Y)
case 0x32: jam(); break; // *JAM
case 0x33: rla_IndirectIndexedY(); break; // *RLA (indirect indexed Y)
case 0x34: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0x35: A() = andr(A(), AM_ZeroPageX()); break; // AND (zero page, X)
case 0x36: memoryReadModifyWrite(rol(AM_ZeroPageX())); break; // ROL (zero page, X)
case 0x37: rla(AM_ZeroPageX()); break; // *RLA (zero page, X)
case 0x38: swallow(); set_flag(CF); break; // SEC (implied)
case 0x39: A() = andr(A(), AM_AbsoluteY()); break; // AND (absolute, Y)
case 0x3a: swallow(); break; // *NOP (implied)
case 0x3b: rla_AbsoluteY(); break; // *RLA (absolute, Y)
case 0x3c: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0x3d: A() = andr(A(), AM_AbsoluteX()); break; // AND (absolute, X)
case 0x3e: memoryReadModifyWrite(rol(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // ROL (absolute, X)
case 0x3f: rla_AbsoluteX(); break; // *RLA (absolute, X)
case 0x40: swallow(); rti(); break; // RTI (implied)
case 0x41: A() = eorr(A(), AM_IndexedIndirectX()); break; // EOR (indexed indirect X)
case 0x42: jam(); break; // *JAM
case 0x43: sre(AM_IndexedIndirectX()); break; // *SRE (indexed indirect X)
case 0x44: AM_ZeroPage(); break; // *NOP (zero page)
case 0x45: A() = eorr(A(), AM_ZeroPage()); break; // EOR (zero page)
case 0x46: memoryReadModifyWrite(lsr(AM_ZeroPage())); break; // LSR (zero page)
case 0x47: sre(AM_ZeroPage()); break; // *SRE (zero page)
case 0x48: swallow(); push(A()); break; // PHA (implied)
case 0x49: A() = eorr(A(), AM_Immediate()); break; // EOR (immediate)
case 0x4a: swallow(); A() = lsr(A()); break; // LSR A (implied)
case 0x4b: asr(AM_Immediate()); break; // *ASR (immediate)
case 0x4c: jump(Address_Absolute()); break; // JMP (absolute)
case 0x4d: A() = eorr(A(), AM_Absolute()); break; // EOR (absolute)
case 0x4e: memoryReadModifyWrite(lsr(AM_Absolute())); break; // LSR (absolute)
case 0x4f: sre(AM_Absolute()); break; // *SRE (absolute)
case 0x50: branch(overflow() == 0); break; // BVC (relative)
case 0x51: A() = eorr(A(), AM_IndirectIndexedY()); break; // EOR (indirect indexed Y)
case 0x52: jam(); break; // *JAM
case 0x53: sre_IndirectIndexedY(); break; // *SRE (indirect indexed Y)
case 0x54: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0x55: A() = eorr(A(), AM_ZeroPageX()); break; // EOR (zero page, X)
case 0x56: memoryReadModifyWrite(lsr(AM_ZeroPageX())); break; // LSR (zero page, X)
case 0x57: sre(AM_ZeroPageX()); break; // *SRE (zero page, X)
case 0x58: swallow(); reset_flag(IF); break; // CLI (implied)
case 0x59: A() = eorr(A(), AM_AbsoluteY()); break; // EOR (absolute, Y)
case 0x5a: swallow(); break; // *NOP (implied)
case 0x5b: sre_AbsoluteY(); break; // *SRE (absolute, Y)
case 0x5c: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0x5d: A() = eorr(A(), AM_AbsoluteX()); break; // EOR (absolute, X)
case 0x5e: memoryReadModifyWrite(lsr(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // LSR (absolute, X)
case 0x5f: sre_AbsoluteX(); break; // *SRE (absolute, X)
case 0x60: swallow(); rts(); break; // RTS (implied)
case 0x61: A() = adc(A(), AM_IndexedIndirectX()); break; // ADC (indexed indirect X)
case 0x62: jam(); break; // *JAM
case 0x63: rra(AM_IndexedIndirectX()); break; // *RRA (indexed indirect X)
case 0x64: AM_ZeroPage(); break; // *NOP (zero page)
case 0x65: A() = adc(A(), AM_ZeroPage()); break; // ADC (zero page)
case 0x66: memoryReadModifyWrite(ror(AM_ZeroPage())); break; // ROR (zero page)
case 0x67: rra(AM_ZeroPage()); break; // *RRA (zero page)
case 0x68: swallow(); swallow_stack(); A() = through(pop()); break; // PLA (implied)
case 0x69: A() = adc(A(), AM_Immediate()); break; // ADC (immediate)
case 0x6a: swallow(); A() = ror(A()); break; // ROR A (implied)
case 0x6b: arr(AM_Immediate()); break; // *ARR (immediate)
case 0x6c: jump(Address_Indirect()); break; // JMP (indirect)
case 0x6d: A() = adc(A(), AM_Absolute()); break; // ADC (absolute)
case 0x6e: memoryReadModifyWrite(ror(AM_Absolute())); break; // ROR (absolute)
case 0x6f: rra(AM_Absolute()); break; // *RRA (absolute)
case 0x70: branch(overflow()); break; // BVS (relative)
case 0x71: A() = adc(A(), AM_IndirectIndexedY()); break; // ADC (indirect indexed Y)
case 0x72: jam(); break; // *JAM
case 0x73: rra_IndirectIndexedY(); break; // *RRA (indirect indexed Y)
case 0x74: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0x75: A() = adc(A(), AM_ZeroPageX()); break; // ADC (zero page, X)
case 0x76: memoryReadModifyWrite(ror(AM_ZeroPageX())); break; // ROR (zero page, X)
case 0x77: rra(AM_ZeroPageX()); break; // *RRA (zero page, X)
case 0x78: swallow(); set_flag(IF); break; // SEI (implied)
case 0x79: A() = adc(A(), AM_AbsoluteY()); break; // ADC (absolute, Y)
case 0x7a: swallow(); break; // *NOP (implied)
case 0x7b: rra_AbsoluteY(); break; // *RRA (absolute, Y)
case 0x7c: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0x7d: A() = adc(A(), AM_AbsoluteX()); break; // ADC (absolute, X)
case 0x7e: memoryReadModifyWrite(ror(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // ROR (absolute, X)
case 0x7f: rra_AbsoluteX(); break; // *RRA (absolute, X)
case 0x80: AM_Immediate(); break; // *NOP (immediate)
case 0x81: memoryWrite(Address_IndexedIndirectX(), A()); break; // STA (indexed indirect X)
case 0x82: AM_Immediate(); break; // *NOP (immediate)
case 0x83: memoryWrite(Address_IndexedIndirectX(), A() & X()); break; // *SAX (indexed indirect X)
case 0x84: memoryWrite(Address_ZeroPage(), Y()); break; // STY (zero page)
case 0x85: memoryWrite(Address_ZeroPage(), A()); break; // STA (zero page)
case 0x86: memoryWrite(Address_ZeroPage(), X()); break; // STX (zero page)
case 0x87: memoryWrite(Address_ZeroPage(), A() & X()); break; // *SAX (zero page)
case 0x88: swallow(); Y() = dec(Y()); break; // DEY (implied)
case 0x89: AM_Immediate(); break; // *NOP (immediate)
case 0x8a: swallow(); A() = through(X()); break; // TXA (implied)
case 0x8b: A() = through((A() | 0xee) & X() & AM_Immediate()); break; // *ANE (immediate)
case 0x8c: memoryWrite(Address_Absolute(), Y()); break; // STY (absolute)
case 0x8d: memoryWrite(Address_Absolute(), A()); break; // STA (absolute)
case 0x8e: memoryWrite(Address_Absolute(), X()); break; // STX (absolute)
case 0x8f: memoryWrite(Address_Absolute(), A() & X()); break; // *SAX (absolute)
case 0x90: branch(carry() == 0); break; // BCC (relative)
case 0x91: sta_IndirectIndexedY(); break; // STA (indirect indexed Y)
case 0x92: jam(); break; // *JAM
case 0x93: sha_IndirectIndexedY(); break; // *SHA (indirect indexed, Y)
case 0x94: memoryWrite(Address_ZeroPageX(), Y()); break; // STY (zero page, X)
case 0x95: memoryWrite(Address_ZeroPageX(), A()); break; // STA (zero page, X)
case 0x96: memoryWrite(Address_ZeroPageY(), X()); break; // STX (zero page, Y)
case 0x97: memoryWrite(Address_ZeroPageY(), A() & X()); break; // *SAX (zero page, Y)
case 0x98: swallow(); A() = through(Y()); break; // TYA (implied)
case 0x99: sta_AbsoluteY(); break; // STA (absolute, Y)
case 0x9a: swallow(); S() = X(); break; // TXS (implied)
case 0x9b: tas_AbsoluteY(); break; // *TAS (absolute, Y)
case 0x9c: sya_AbsoluteX(); break; // *SYA (absolute, X)
case 0x9d: sta_AbsoluteX(); break; // STA (absolute, X)
case 0x9e: sxa_AbsoluteY(); break; // *SXA (absolute, Y)
case 0x9f: sha_AbsoluteY(); break; // *SHA (absolute, Y)
case 0xa0: Y() = through(AM_Immediate()); break; // LDY (immediate)
case 0xa1: A() = through(AM_IndexedIndirectX()); break; // LDA (indexed indirect X)
case 0xa2: X() = through(AM_Immediate()); break; // LDX (immediate)
case 0xa3: A() = X() = through(AM_IndexedIndirectX()); break; // *LAX (indexed indirect X)
case 0xa4: Y() = through(AM_ZeroPage()); break; // LDY (zero page)
case 0xa5: A() = through(AM_ZeroPage()); break; // LDA (zero page)
case 0xa6: X() = through(AM_ZeroPage()); break; // LDX (zero page)
case 0xa7: A() = X() = through(AM_ZeroPage()); break; // *LAX (zero page)
case 0xa8: swallow(); Y() = through(A()); break; // TAY (implied)
case 0xa9: A() = through(AM_Immediate()); break; // LDA (immediate)
case 0xaa: swallow(); X() = through(A()); break; // TAX (implied)
case 0xab: A() = X() = through((A() | 0xee) & AM_Immediate()); break; // *ATX (immediate)
case 0xac: Y() = through(AM_Absolute()); break; // LDY (absolute)
case 0xad: A() = through(AM_Absolute()); break; // LDA (absolute)
case 0xae: X() = through(AM_Absolute()); break; // LDX (absolute)
case 0xaf: A() = X() = through(AM_Absolute()); break; // *LAX (absolute)
case 0xb0: branch(carry()); break; // BCS (relative)
case 0xb1: A() = through(AM_IndirectIndexedY()); break; // LDA (indirect indexed Y)
case 0xb2: jam(); break; // *JAM
case 0xb3: A() = X() = through(AM_IndirectIndexedY()); break; // *LAX (indirect indexed Y)
case 0xb4: Y() = through(AM_ZeroPageX()); break; // LDY (zero page, X)
case 0xb5: A() = through(AM_ZeroPageX()); break; // LDA (zero page, X)
case 0xb6: X() = through(AM_ZeroPageY()); break; // LDX (zero page, Y)
case 0xb7: A() = X() = through(AM_ZeroPageY()); break; // *LAX (zero page, Y)
case 0xb8: swallow(); reset_flag(VF); break; // CLV (implied)
case 0xb9: A() = through(AM_AbsoluteY()); break; // LDA (absolute, Y)
case 0xba: swallow(); X() = through(S()); break; // TSX (implied)
case 0xbb: las_AbsoluteY(); break; // *LAS (absolute, Y)
case 0xbc: Y() = through(AM_AbsoluteX()); break; // LDY (absolute, X)
case 0xbd: A() = through(AM_AbsoluteX()); break; // LDA (absolute, X)
case 0xbe: X() = through(AM_AbsoluteY()); break; // LDX (absolute, Y)
case 0xbf: A() = X() = through(AM_AbsoluteY()); break; // *LAX (absolute, Y)
case 0xc0: cmp(Y(), AM_Immediate()); break; // CPY (immediate)
case 0xc1: cmp(A(), AM_IndexedIndirectX()); break; // CMP (indexed indirect X)
case 0xc2: AM_Immediate(); break; // *NOP (immediate)
case 0xc3: dcp(AM_IndexedIndirectX()); break; // *DCP (indexed indirect X)
case 0xc4: cmp(Y(), AM_ZeroPage()); break; // CPY (zero page)
case 0xc5: cmp(A(), AM_ZeroPage()); break; // CMP (zero page)
case 0xc6: memoryReadModifyWrite(dec(AM_ZeroPage())); break; // DEC (zero page)
case 0xc7: dcp(AM_ZeroPage()); break; // *DCP (zero page)
case 0xc8: swallow(); Y() = inc(Y()); break; // INY (implied)
case 0xc9: cmp(A(), AM_Immediate()); break; // CMP (immediate)
case 0xca: swallow(); X() = dec(X()); break; // DEX (implied)
case 0xcb: axs(AM_Immediate()); break; // *AXS (immediate)
case 0xcc: cmp(Y(), AM_Absolute()); break; // CPY (absolute)
case 0xcd: cmp(A(), AM_Absolute()); break; // CMP (absolute)
case 0xce: memoryReadModifyWrite(dec(AM_Absolute())); break; // DEC (absolute)
case 0xcf: dcp(AM_Absolute()); break; // *DCP (absolute)
case 0xd0: branch(zero() == 0); break; // BNE (relative)
case 0xd1: cmp(A(), AM_IndirectIndexedY()); break; // CMP (indirect indexed Y)
case 0xd2: jam(); break; // *JAM
case 0xd3: dcp_IndirectIndexedY(); break; // *DCP (indirect indexed Y)
case 0xd4: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0xd5: cmp(A(), AM_ZeroPageX()); break; // CMP (zero page, X)
case 0xd6: memoryReadModifyWrite(dec(AM_ZeroPageX())); break; // DEC (zero page, X)
case 0xd7: dcp(AM_ZeroPageX()); break; // *DCP (zero page, X)
case 0xd8: swallow(); reset_flag(DF); break; // CLD (implied)
case 0xd9: cmp(A(), AM_AbsoluteY()); break; // CMP (absolute, Y)
case 0xda: swallow(); break; // *NOP (implied)
case 0xdb: dcp_AbsoluteY(); break; // *DCP (absolute, Y)
case 0xdc: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0xdd: cmp(A(), AM_AbsoluteX()); break; // CMP (absolute, X)
case 0xde: memoryReadModifyWrite(dec(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // DEC (absolute, X)
case 0xdf: dcp_AbsoluteX(); break; // *DCP (absolute, X)
case 0xe0: cmp(X(), AM_Immediate()); break; // CPX (immediate)
case 0xe1: A() = sbc(A(), AM_IndexedIndirectX()); break; // SBC (indexed indirect X)
case 0xe2: AM_Immediate(); break; // *NOP (immediate)
case 0xe3: isb(AM_IndexedIndirectX()); break; // *ISB (indexed indirect X)
case 0xe4: cmp(X(), AM_ZeroPage()); break; // CPX (zero page)
case 0xe5: A() = sbc(A(), AM_ZeroPage()); break; // SBC (zero page)
case 0xe6: memoryReadModifyWrite(inc(AM_ZeroPage())); break; // INC (zero page)
case 0xe7: isb(AM_ZeroPage()); break; // *ISB (zero page)
case 0xe8: swallow(); X() = inc(X()); break; // INX (implied)
case 0xe9: A() = sbc(A(), AM_Immediate()); break; // SBC (immediate)
case 0xea: swallow(); break; // NOP (implied)
case 0xeb: A() = sbc(A(), AM_Immediate()); break; // *SBC (immediate)
case 0xec: cmp(X(), AM_Absolute()); break; // CPX (absolute)
case 0xed: A() = sbc(A(), AM_Absolute()); break; // SBC (absolute)
case 0xee: memoryReadModifyWrite(inc(AM_Absolute())); break; // INC (absolute)
case 0xef: isb(AM_Absolute()); break; // *ISB (absolute)
case 0xf0: branch(zero()); break; // BEQ (relative)
case 0xf1: A() = sbc(A(), AM_IndirectIndexedY()); break; // SBC (indirect indexed Y)
case 0xf2: jam(); break; // *JAM
case 0xf3: isb_IndirectIndexedY(); break; // *ISB (indirect indexed Y)
case 0xf4: AM_ZeroPageX(); break; // *NOP (zero page, X)
case 0xf5: A() = sbc(A(), AM_ZeroPageX()); break; // SBC (zero page, X)
case 0xf6: memoryReadModifyWrite(inc(AM_ZeroPageX())); break; // INC (zero page, X)
case 0xf7: isb(AM_ZeroPageX()); break; // *ISB (zero page, X)
case 0xf8: swallow(); set_flag(DF); break; // SED (implied)
case 0xf9: A() = sbc(A(), AM_AbsoluteY()); break; // SBC (absolute, Y)
case 0xfa: swallow(); break; // *NOP (implied)
case 0xfb: isb_AbsoluteY(); break; // *ISB (absolute, Y)
case 0xfc: nop_AbsoluteX(); break; // *NOP (absolute, X)
case 0xfd: A() = sbc(A(), AM_AbsoluteX()); break; // SBC (absolute, X)
case 0xfe: memoryReadModifyWrite(inc(AM_AbsoluteX(PageCrossingBehavior::AlwaysReadTwice))); break; // INC (absolute, X)
case 0xff: isb_AbsoluteX(); break; // *ISB (absolute, X)
}
ASSUME(cycles() > 0);
return cycles();
}
////
void EightBit::MOS6502::push(uint8_t value) noexcept {
setBytePaged(1, S()--, value);
}
uint8_t EightBit::MOS6502::pop() noexcept {
return getBytePaged(1, ++S());
}
void EightBit::MOS6502::dummyPush(const uint8_t value) noexcept {
tick();
BUS().DATA() = value;
BUS().ADDRESS() = { S()--, 1 };
}
////
EightBit::register16_t EightBit::MOS6502::Address_Immediate() noexcept {
return PC()++;
}
EightBit::register16_t EightBit::MOS6502::Address_Absolute() noexcept {
return fetchWord();
}
uint8_t EightBit::MOS6502::Address_ZeroPage() noexcept {
return fetchByte();
}
EightBit::register16_t EightBit::MOS6502::Address_ZeroPageIndirect() noexcept {
BUS().ADDRESS() = { Address_ZeroPage(), 0 };
return getWordPaged();
}
EightBit::register16_t EightBit::MOS6502::Address_Indirect() noexcept {
BUS().ADDRESS() = Address_Absolute();
return getWordPaged();
}
uint8_t EightBit::MOS6502::Address_ZeroPageX() noexcept {
const auto address = Address_ZeroPage();
memoryRead(address);
return address + X();
}
uint8_t EightBit::MOS6502::Address_ZeroPageY() noexcept {
const auto address = Address_ZeroPage();
memoryRead(address);
return address + Y();
}
std::pair<EightBit::register16_t, uint8_t> EightBit::MOS6502::Address_AbsoluteX() noexcept {
const auto address = Address_Absolute();
const auto page = address.high;
return { address + X(), page };
}
std::pair<EightBit::register16_t, uint8_t> EightBit::MOS6502::Address_AbsoluteY() noexcept {
const auto address = Address_Absolute();
const auto page = address.high;
return { address + Y(), page };
}
EightBit::register16_t EightBit::MOS6502::Address_IndexedIndirectX() noexcept {
BUS().ADDRESS() = { Address_ZeroPageX(), 0 };
return getWordPaged();
}
std::pair<EightBit::register16_t, uint8_t> EightBit::MOS6502::Address_IndirectIndexedY() noexcept {
const auto address = Address_ZeroPageIndirect();
const auto page = address.high;
return { address + Y(), page };
}
EightBit::register16_t EightBit::MOS6502::Address_relative_byte() noexcept {
return PC() + (int8_t)fetchByte();
}
// Addressing modes, read
uint8_t EightBit::MOS6502::AM_Immediate() noexcept {
return memoryRead(Address_Immediate());
}
uint8_t EightBit::MOS6502::AM_Absolute() noexcept {
return memoryRead(Address_Absolute());
}
uint8_t EightBit::MOS6502::AM_ZeroPage() noexcept {
return memoryRead(Address_ZeroPage());
}
uint8_t EightBit::MOS6502::AM_AbsoluteX(const PageCrossingBehavior behaviour) noexcept {
const auto [address, page] = Address_AbsoluteX();
maybe_fixup(address, page, behaviour == PageCrossingBehavior::AlwaysReadTwice);
return memoryRead();
}
uint8_t EightBit::MOS6502::AM_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
maybe_fixup(address, page);
return memoryRead();
}
uint8_t EightBit::MOS6502::AM_ZeroPageX() noexcept {
return memoryRead(Address_ZeroPageX());
}
uint8_t EightBit::MOS6502::AM_ZeroPageY() noexcept {
return memoryRead(Address_ZeroPageY());
}
uint8_t EightBit::MOS6502::AM_IndexedIndirectX() noexcept {
return memoryRead(Address_IndexedIndirectX());
}
uint8_t EightBit::MOS6502::AM_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
maybe_fixup(address, page);
return memoryRead();
}
////
void EightBit::MOS6502::branch(const int condition) noexcept {
const auto destination = Address_relative_byte();
if (condition) {
swallow();
const auto page = PC().high;
jump(destination);
maybe_fixup(PC(), page);
}
}
////
uint8_t EightBit::MOS6502::sbc(const uint8_t operand, const uint8_t data) noexcept {
const auto returned = sub(operand, data, carry(~P()));
const auto difference = m_intermediate;
adjustNZ(difference.low);
adjustOverflow_subtract(operand, data, difference.low);
reset_flag(CF, difference.high);
return returned;
}
uint8_t EightBit::MOS6502::sub(const uint8_t operand, const uint8_t data, const int borrow) noexcept {
return decimal() ? sub_d(operand, data, borrow) : sub_b(operand, data, borrow);
}
uint8_t EightBit::MOS6502::sub_b(const uint8_t operand, const uint8_t data, const int borrow) noexcept {
m_intermediate.word = operand - data - borrow;
return m_intermediate.low;
}
uint8_t EightBit::MOS6502::sub_d(const uint8_t operand, const uint8_t data, const int borrow) noexcept {
m_intermediate.word = operand - data - borrow;
uint8_t low = lowNibble(operand) - lowNibble(data) - borrow;
const auto lowNegative = negative(low);
if (lowNegative)
low -= 6;
uint8_t high = highNibble(operand) - highNibble(data) - (lowNegative >> 7);
const auto highNegative = negative(high);
if (highNegative)
high -= 6;
return promoteNibble(high) | lowNibble(low);
}
uint8_t EightBit::MOS6502::adc(const uint8_t operand, const uint8_t data) noexcept {
return add(operand, data, carry());
}
uint8_t EightBit::MOS6502::add(uint8_t operand, uint8_t data, int carrying) noexcept {
return decimal() ? add_d(operand, data, carrying) : add_b(operand, data, carrying);
}
uint8_t EightBit::MOS6502::add_b(uint8_t operand, uint8_t data, int carrying) noexcept {
m_intermediate.word = operand + data + carrying;
adjustOverflow_add(operand, data, m_intermediate.low);
set_flag(CF, carry(m_intermediate.high));
adjustNZ(m_intermediate.low);
return m_intermediate.low;
}
uint8_t EightBit::MOS6502::add_d(uint8_t operand, uint8_t data, int carry) noexcept {
register16_t low = lowerNibble(operand) + lowerNibble(data) + carry;
register16_t high = higherNibble(operand) + higherNibble(data);
adjustZero((low + high).low);
if (low.word > 0x09) {
high += 0x10;
low += 0x06;
}
adjustNegative(high.low);
adjustOverflow_add(operand, data, high.low);
if (high.word > 0x90)
high += 0x60;
set_flag(CF, high.high);
return lowerNibble(low.low) | higherNibble(high.low);
}
uint8_t EightBit::MOS6502::andr(const uint8_t operand, const uint8_t data) noexcept {
return through(operand & data);
}
void EightBit::MOS6502::bit(const uint8_t operand, const uint8_t data) noexcept {
set_flag(VF, overflow(data));
adjustZero(operand & data);
adjustNegative(data);
}
void EightBit::MOS6502::cmp(const uint8_t first, const uint8_t second) noexcept {
const register16_t result = first - second;
adjustNZ(result.low);
reset_flag(CF, result.high);
}
uint8_t EightBit::MOS6502::dec(const uint8_t value) noexcept {
return through(value - 1);
}
uint8_t EightBit::MOS6502::eorr(const uint8_t operand, const uint8_t data) noexcept {
return through(operand ^ data);
}
uint8_t EightBit::MOS6502::inc(const uint8_t value) noexcept {
return through(value + 1);
}
void EightBit::MOS6502::jsr() noexcept {
const auto low = fetchByte();
swallow_stack();
pushWord(PC());
PC().high = fetchByte();
PC().low = low;
}
uint8_t EightBit::MOS6502::orr(const uint8_t operand, const uint8_t data) noexcept {
return through(operand | data);
}
void EightBit::MOS6502::php() noexcept {
push(P() | BF);
}
void EightBit::MOS6502::plp() noexcept {
swallow_stack();
P() = (pop() | RF) & ~BF;
}
void EightBit::MOS6502::rti() noexcept {
plp();
ret();
}
void EightBit::MOS6502::rts() noexcept {
swallow_stack();
ret();
swallow_fetch();
}
// Undocumented compound instructions
void EightBit::MOS6502::anc(const uint8_t value) noexcept {
A() = andr(A(), value);
set_flag(CF, A() & Bit7);
}
void EightBit::MOS6502::arr(const uint8_t value) noexcept {
decimal() ? arr_d(value) : arr_b(value);
}
void EightBit::MOS6502::arr_d(const uint8_t value) noexcept {
// With thanks to https://github.com/TomHarte/CLK
// What a very strange instruction ARR is...
A() &= value;
auto unshiftedA = A();
A() = through((A() >> 1) | (carry() << 7));
set_flag(VF, overflow((A() ^ (A() << 1))));
if (lowerNibble(unshiftedA) + (unshiftedA & 0x1) > 5)
A() = lowerNibble(A() + 6) | higherNibble(A());
set_flag(CF, higherNibble(unshiftedA) + (unshiftedA & 0x10) > 0x50);
if (carry())
A() += 0x60;
}
void EightBit::MOS6502::arr_b(const uint8_t value) noexcept {
A() &= value;
A() = through((A() >> 1) | (carry() << 7));
set_flag(CF, A() & Bit6);
set_flag(VF, overflow((A() ^ (A() << 1))));
}
void EightBit::MOS6502::asr(const uint8_t value) noexcept {
A() = andr(A(), value);
A() = lsr(A());
}
void EightBit::MOS6502::axs(const uint8_t value) noexcept {
X() = through(sub_b(A() & X(), value));
reset_flag(CF, m_intermediate.high);
}
void EightBit::MOS6502::dcp(const uint8_t value) noexcept {
memoryReadModifyWrite(dec(value));
cmp(A(), BUS().DATA());
}
void EightBit::MOS6502::isb(const uint8_t value) noexcept {
memoryReadModifyWrite(inc(value));
A() = sbc(A(), BUS().DATA());
}
void EightBit::MOS6502::rla(const uint8_t value) noexcept {
memoryReadModifyWrite(rol(value));
A() = andr(A(), BUS().DATA());
}
void EightBit::MOS6502::rra(const uint8_t value) noexcept {
memoryReadModifyWrite(ror(value));
A() = adc(A(), BUS().DATA());
}
void EightBit::MOS6502::slo(const uint8_t value) noexcept {
memoryReadModifyWrite(asl(value));
A() = orr(A(), BUS().DATA());
}
void EightBit::MOS6502::sre(const uint8_t value) noexcept {
memoryReadModifyWrite(lsr(value));
A() = eorr(A(), BUS().DATA());
}
void EightBit::MOS6502::jam() noexcept {
swallow();
swallow();
--PC();
}
//
void EightBit::MOS6502::sta_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
sta_with_fixup(address, page);
}
void EightBit::MOS6502::sta_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
sta_with_fixup(address, page);
}
void EightBit::MOS6502::sta_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
sta_with_fixup(address, page);
}
//
void EightBit::MOS6502::slo_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
slo_with_fixup(address, page);
}
void EightBit::MOS6502::slo_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
slo_with_fixup(address, page);
}
void EightBit::MOS6502::slo_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
slo_with_fixup(address, page);
}
void EightBit::MOS6502::isb_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
isb_with_fixup(address, page);
}
void EightBit::MOS6502::isb_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
isb_with_fixup(address, page);
}
void EightBit::MOS6502::isb_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
isb_with_fixup(address, page);
}
void EightBit::MOS6502::rla_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
rla_with_fixup(address, page);
}
void EightBit::MOS6502::rla_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
rla_with_fixup(address, page);
}
void EightBit::MOS6502::rla_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
rla_with_fixup(address, page);
}
void EightBit::MOS6502::rra_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
rra_with_fixup(address, page);
}
void EightBit::MOS6502::rra_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
rra_with_fixup(address, page);
}
void EightBit::MOS6502::rra_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
rra_with_fixup(address, page);
}
void EightBit::MOS6502::dcp_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
dcp_with_fixup(address, page);
}
void EightBit::MOS6502::dcp_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
dcp_with_fixup(address, page);
}
void EightBit::MOS6502::dcp_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
dcp_with_fixup(address, page);
}
void EightBit::MOS6502::sre_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
sre_with_fixup(address, page);
}
void EightBit::MOS6502::sre_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
sre_with_fixup(address, page);
}
void EightBit::MOS6502::sre_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
sre_with_fixup(address, page);
}
void EightBit::MOS6502::sha_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
fixup(address, page);
memoryWrite(address, A() & X() & (address.high + 1));
}
void EightBit::MOS6502::sha_IndirectIndexedY() noexcept {
const auto [address, page] = Address_IndirectIndexedY();
fixup(address, page);
memoryWrite(address, A() & X() & (address.high + 1));
}
void EightBit::MOS6502::sya_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
fixup(address, page);
memoryWrite(Y() & (address.high + 1));
}
void EightBit::MOS6502::tas_AbsoluteY() noexcept {
S() = A() & X();
sha_AbsoluteY();
}
void EightBit::MOS6502::las_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
maybe_fixup(address, page);
A() = X() = S() = through(memoryRead(address) & S());
}
void EightBit::MOS6502::sxa_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
fixup(address, page);
memoryWrite(X() & (address.high + 1));
}
void EightBit::MOS6502::nop_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
fixup(address, page);
}
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