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Implementing ROR

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This commit is contained in:
Anonymus Raccoon
2020-05-13 16:35:13 +02:00
parent deab98dac0
commit 4c4cc6b655
3 changed files with 103 additions and 5 deletions
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sources/CPU/Instructions/BitsInstructions.cpp
+42
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@@ -176,4 +176,46 @@ namespace ComSquare::CPU
}
return cycles;
}
int CPU::ROR(uint24_t valueAddr, AddressingMode mode)
{
this->_registers.p.n = false;
bool oldCarry = this->_registers.p.c;
unsigned highByteIndex = this->_registers.p.m ? 7 : 15;
if (mode == Implied) {
this->_registers.p.c = this->_registers.a & 1u;
this->_registers.a >>= 1u;
this->_registers.a |= oldCarry << highByteIndex;
this->_registers.p.z = this->_registers.a == 0;
return 0;
}
uint16_t value = this->_bus->read(valueAddr);
if (!this->_registers.p.m)
value += this->_bus->read(valueAddr + 1) << 8u;
this->_registers.p.c = value & 1u;
value >>= 1u;
value |= oldCarry << highByteIndex;
this->_registers.p.z = value == 0;
this->_bus->write(valueAddr, value);
if (!this->_registers.p.m)
this->_bus->write(valueAddr + 1, value >> 8u);
int cycles = 2 * !this->_registers.p.m;
switch (mode) {
case DirectPage:
case DirectPageIndexedByX:
cycles += this->_registers.dl != 0;
break;
case AbsoluteIndexedByX:
cycles += this->_hasIndexCrossedPageBoundary;
break;
default:
break;
}
return cycles;
}
}