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Cycle accuracy changes for BRK/RTI instructions.

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2019-01-06 11:13:49 +00:00
parent 5b9c348ff1
commit 3749585398
1 changed files with 10 additions and 7 deletions
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17
M6502/src/mos6502.cpp
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@ -96,7 +96,7 @@ int EightBit::MOS6502::execute() {
switch (opcode()) { switch (opcode()) {
case 0x00: brk(); break; // BRK (implied) case 0x00: fetchByte(); brk(); break; // BRK (implied)
case 0x01: A() = orr(A(), AM_IndexedIndirectX()); break; // ORA (indexed indirect X) case 0x01: A() = orr(A(), AM_IndexedIndirectX()); break; // ORA (indexed indirect X)
case 0x02: break; case 0x02: break;
case 0x03: slo(AM_IndexedIndirectX()); break; // *SLO (indexed indirect X) case 0x03: slo(AM_IndexedIndirectX()); break; // *SLO (indexed indirect X)
@ -164,7 +164,7 @@ int EightBit::MOS6502::execute() {
case 0x3e: addCycle(); busReadModifyWrite(rol(AM_AbsoluteX())); break; // ROL (absolute, X) case 0x3e: addCycle(); busReadModifyWrite(rol(AM_AbsoluteX())); break; // ROL (absolute, X)
case 0x3f: rla(AM_AbsoluteX()); break; // *RLA (absolute, X) case 0x3f: rla(AM_AbsoluteX()); break; // *RLA (absolute, X)
case 0x40: addCycles(2); rti(); break; // RTI (implied) case 0x40: busRead(); rti(); break; // RTI (implied)
case 0x41: A() = eorr(A(), AM_IndexedIndirectX()); break; // EOR (indexed indirect X) case 0x41: A() = eorr(A(), AM_IndexedIndirectX()); break; // EOR (indexed indirect X)
case 0x42: break; case 0x42: break;
case 0x43: sre(AM_IndexedIndirectX()); break; // *SRE (indexed indirect X) case 0x43: sre(AM_IndexedIndirectX()); break; // *SRE (indexed indirect X)
@ -403,13 +403,15 @@ EightBit::register16_t EightBit::MOS6502::Address_Indirect() {
} }
uint8_t EightBit::MOS6502::Address_ZeroPageX() { uint8_t EightBit::MOS6502::Address_ZeroPageX() {
addCycle(); const auto address = Address_ZeroPage();
return Address_ZeroPage() + X(); Processor::busRead(address);
return address + X();
} }
uint8_t EightBit::MOS6502::Address_ZeroPageY() { uint8_t EightBit::MOS6502::Address_ZeroPageY() {
addCycle(); const auto address = Address_ZeroPage();
return Address_ZeroPage() + Y(); Processor::busRead(address);
return address + Y();
} }
std::pair<EightBit::register16_t, bool> EightBit::MOS6502::Address_AbsoluteX() { std::pair<EightBit::register16_t, bool> EightBit::MOS6502::Address_AbsoluteX() {
@ -594,7 +596,7 @@ void EightBit::MOS6502::bit(const uint8_t operand, const uint8_t data) {
} }
void EightBit::MOS6502::brk() { void EightBit::MOS6502::brk() {
pushWord(++PC()); pushWord(PC());
php(); php();
setFlag(P(), IF); setFlag(P(), IF);
jump(getWordPaged(0xff, IRQvector)); jump(getWordPaged(0xff, IRQvector));
@ -658,6 +660,7 @@ uint8_t EightBit::MOS6502::ror(const uint8_t operand) {
} }
void EightBit::MOS6502::rti() { void EightBit::MOS6502::rti() {
getBytePaged(1, S()); // dummy read
plp(); plp();
ret(); ret();
} }