mirror of
https://github.com/zoriya/ComSquare.git
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93 lines
2.8 KiB
C++
93 lines
2.8 KiB
C++
//
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// Created by anonymus-raccoon on 2/10/20.
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//
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#include <iostream>
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#include "../CPU.hpp"
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namespace ComSquare::CPU
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{
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int CPU::ADC(uint24_t valueAddr, AddressingMode mode)
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{
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unsigned value = this->_bus->read(valueAddr) + this->_registers.p.c;
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if (!this->_registers.p.m)
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value += this->_bus->read(valueAddr + 1) << 8u;
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unsigned negativeMask = this->_isEmulationMode ? 0x80u : 0x8000u;
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unsigned maxValue = this->_isEmulationMode ? UINT8_MAX : UINT16_MAX;
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this->_registers.p.c = static_cast<unsigned>(this->_registers.a) + value > maxValue;
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if ((this->_registers.a & negativeMask) == (value & negativeMask))
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this->_registers.p.v = (this->_registers.a & negativeMask) != ((this->_registers.a + value) & negativeMask);
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else
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this->_registers.p.v = false;
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this->_registers.a += value;
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if (this->_isEmulationMode)
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this->_registers.a %= 0x100;
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this->_registers.p.z = this->_registers.a == 0;
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this->_registers.p.n = this->_registers.a & negativeMask;
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int cycles = !this->_registers.p.m;
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switch (mode) {
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case DirectPage:
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case DirectPageIndirect:
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case DirectPageIndirectLong:
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case DirectPageIndexedByX:
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case DirectPageIndirectIndexedByX:
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case DirectPageIndirectIndexedByYLong:
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cycles += this->_registers.dl != 0;
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break;
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case AbsoluteIndexedByX:
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case AbsoluteIndexedByY:
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cycles += this->_hasIndexCrossedPageBoundary;
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break;
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case DirectPageIndirectIndexedByY:
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cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
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break;
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default:
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break;
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}
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return cycles;
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}
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int CPU::SBC(uint24_t valueAddr, AddressingMode mode)
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{
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unsigned negativeMask = this->_isEmulationMode ? 0x80u : 0x8000u;
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unsigned value = this->_bus->read(valueAddr);
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if (!this->_registers.p.m)
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value += this->_bus->read(valueAddr + 1) << 8u;
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bool oldCarry = this->_registers.p.c;
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this->_registers.p.c = this->_registers.a >= value;
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if ((this->_registers.a & negativeMask) == (value & negativeMask))
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this->_registers.p.v = (this->_registers.a & negativeMask) != ((this->_registers.a + value) & negativeMask);
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else
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this->_registers.p.v = false;
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this->_registers.a += ~value + oldCarry;
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if (this->_isEmulationMode)
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this->_registers.a %= 0x100;
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this->_registers.p.z = this->_registers.a == 0;
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this->_registers.p.n = this->_registers.a & negativeMask;
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int cycles = !this->_registers.p.m;
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switch (mode) {
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case DirectPage:
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case DirectPageIndirect:
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case DirectPageIndirectLong:
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case DirectPageIndexedByX:
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case DirectPageIndirectIndexedByX:
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case DirectPageIndirectIndexedByYLong:
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cycles += this->_registers.dl != 0;
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break;
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case AbsoluteIndexedByX:
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case AbsoluteIndexedByY:
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cycles += this->_hasIndexCrossedPageBoundary;
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break;
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case DirectPageIndirectIndexedByY:
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cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
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break;
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default:
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break;
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}
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return cycles;
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}
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} |