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Implementing the LDX

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This commit is contained in:
AnonymusRaccoon
2020-02-13 17:42:41 +01:00
parent 6fca2293ee
commit 9cf41e6ff4
4 changed files with 53 additions and 26 deletions
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sources/CPU/CPU.cpp
+6
View File
@@ -265,6 +265,12 @@ namespace ComSquare::CPU
case Instructions::LDA_SR: this->LDA(this->_getStackRelativeAddr()); return 4 + !this->_registers.p.m;
case Instructions::LDA_SRYi: this->LDA(this->_getStackRelativeIndirectIndexedYAddr()); return 7 + !this->_registers.p.m;
case Instructions::LDX_IM: this->LDX(this->_getImmediateAddr()); return 2 + !this->_registers.p.m;
case Instructions::LDX_ABS: this->LDX(this->_getAbsoluteAddr()); return 4 + !this->_registers.p.m;
case Instructions::LDX_DP: this->LDX(this->_getDirectAddr()); return 3 + !this->_registers.p.m + this->_registers.dl != 0;
case Instructions::LDX_ABSY: this->LDX(this->_getAbsoluteIndexedByYAddr()); return 4 + !this->_registers.p.m + this->_hasIndexCrossedPageBoundary;
case Instructions::LDX_DPY: this->LDX(this->_getDirectIndexedByYAddr()); return 4 + !this->_registers.p.m + this->_registers.dl != 0;
default:
throw InvalidOpcode("CPU", opcode);
}
sources/CPU/CPU.hpp
+9 -1
View File
@@ -247,7 +247,13 @@ namespace ComSquare::CPU
LDA_DPYi = 0xB1,
LDA_DPYil = 0xB7,
LDA_SR = 0xA3,
LDA_SRYi = 0xB3
LDA_SRYi = 0xB3,
LDX_IM = 0xA2,
LDX_ABS = 0xAE,
LDX_DP = 0xA6,
LDX_ABSY = 0xBE,
LDX_DPY = 0xB6
};
//! @brief The main CPU
@@ -342,6 +348,8 @@ namespace ComSquare::CPU
void STZ(uint24_t addr);
//! @brief Load the accumulator from memory.
void LDA(uint24_t addr);
//! @brief Load the X index register from memory.
void LDX(uint24_t addr);
public:
explicit CPU(std::shared_ptr<Memory::MemoryBus> bus, Cartridge::Header &cartridgeHeader);
CPU(const CPU &) = default;
sources/CPU/Instructions/MemoryInstructions.cpp
+13
View File
@@ -55,4 +55,17 @@ namespace ComSquare::CPU
}
this->_registers.p.z = this->_registers.a == 0x0;
}
void CPU::LDX(uint24_t addr)
{
if (this->_registers.p.x_b) {
this->_registers.x = this->_bus->read(addr);
this->_registers.p.n = this->_registers.xl & 0xF0u;
} else {
this->_registers.xl = this->_bus->read(addr);
this->_registers.xh = this->_bus->read(addr + 1);
this->_registers.p.n = this->_registers.x & 0xF000u;
}
this->_registers.p.z = this->_registers.x == 0x0;
}
}