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Implementing DEX & DEY

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This commit is contained in:
Anonymus Raccoon
2020-04-03 15:14:19 +02:00
parent 7407c3cfaa
commit 9f8ae6cb08
4 changed files with 39 additions and 11 deletions
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sources/CPU/Instructions/MathematicalOperations.cpp
+29 -5
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@@ -12,8 +12,8 @@ namespace ComSquare::CPU
unsigned value = this->_bus->read(valueAddr) + this->_registers.p.c;
if (!this->_registers.p.m)
value += this->_bus->read(valueAddr + 1) << 8u;
unsigned negativeMask = this->_isEmulationMode ? 0x80u : 0x8000u;
unsigned maxValue = this->_isEmulationMode ? UINT8_MAX : UINT16_MAX;
unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
unsigned maxValue = this->_registers.p.m ? UINT8_MAX : UINT16_MAX;
this->_registers.p.c = static_cast<unsigned>(this->_registers.a) + value > maxValue;
if ((this->_registers.a & negativeMask) == (value & negativeMask))
@@ -21,7 +21,7 @@ namespace ComSquare::CPU
else
this->_registers.p.v = false;
this->_registers.a += value;
if (this->_isEmulationMode)
if (this->_registers.p.m)
this->_registers.a %= 0x100;
this->_registers.p.z = this->_registers.a == 0;
this->_registers.p.n = this->_registers.a & negativeMask;
@@ -51,7 +51,7 @@ namespace ComSquare::CPU
int CPU::SBC(uint24_t valueAddr, AddressingMode mode)
{
unsigned negativeMask = this->_isEmulationMode ? 0x80u : 0x8000u;
unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
unsigned value = this->_bus->read(valueAddr);
if (!this->_registers.p.m)
value += this->_bus->read(valueAddr + 1) << 8u;
@@ -63,7 +63,7 @@ namespace ComSquare::CPU
else
this->_registers.p.v = false;
this->_registers.a += ~value + oldCarry;
if (this->_isEmulationMode)
if (this->_registers.p.m)
this->_registers.a %= 0x100;
this->_registers.p.z = this->_registers.a == 0;
this->_registers.p.n = this->_registers.a & negativeMask;
@@ -90,4 +90,28 @@ namespace ComSquare::CPU
}
return cycles;
}
int CPU::DEX(uint24_t, AddressingMode)
{
unsigned negativeMask = this->_registers.p.x_b ? UINT8_MAX : UINT16_MAX;
this->_registers.x--;
if (this->_registers.p.x_b)
this->_registers.xh = 0;
this->_registers.p.z = this->_registers.x == 0;
this->_registers.p.n = this->_registers.x & negativeMask;
return 0;
}
int CPU::DEY(uint24_t, AddressingMode)
{
unsigned negativeMask = this->_registers.p.x_b ? UINT8_MAX : UINT16_MAX;
this->_registers.y--;
if (this->_registers.p.x_b)
this->_registers.yh = 0;
this->_registers.p.z = this->_registers.y == 0;
this->_registers.p.n = this->_registers.y & negativeMask;
return 0;
}
}