272 lines
8.9 KiB
C++
272 lines
8.9 KiB
C++
/*
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* This file is part of the 65816 Emulator Library.
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* Copyright (c) 2018 Francesco Rigoni.
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*
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* https://github.com/FrancescoRigoni/Lib65816
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "../Cpu65816.hpp"
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#define LOG_TAG "Cpu::executeADC"
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/**
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* This file contains the implementation for all ADC OpCodes.
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*/
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void Cpu65816::execute8BitADC(OpCode &opCode) {
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Address dataAddress = getAddressOfOpCodeData(opCode);
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uint8_t value = mSystemBus.readByte(dataAddress);
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uint8_t accumulator = Binary::lower8BitsOf(mA);
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uint8_t carryValue = mCpuStatus.carryFlag() ? 1 : 0;
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uint16_t result16Bit = accumulator + value + carryValue;
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// Is there a carry out of the penultimate bit, redo the sum with 7 bits value and find out.
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accumulator &= 0x7F;
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value &= 0x7F;
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uint8_t partialResult = accumulator + value + carryValue;
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// Is bit 8 set?
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bool carryOutOfPenultimateBit = partialResult & 0x80;
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// Is there a carry out of the last bit, check bit 8 for that
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bool carryOutOfLastBit = result16Bit & 0x0100;
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bool overflow = carryOutOfLastBit ^ carryOutOfPenultimateBit;
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if (overflow) mCpuStatus.setOverflowFlag();
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else mCpuStatus.clearOverflowFlag();
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if (carryOutOfLastBit) mCpuStatus.setCarryFlag();
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else mCpuStatus.clearCarryFlag();
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uint8_t result8Bit = Binary::lower8BitsOf(result16Bit);
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// Update sign and zero flags
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mCpuStatus.updateSignAndZeroFlagFrom8BitValue(result8Bit);
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// Store the 8 bit result in the accumulator
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Binary::setLower8BitsOf16BitsValue(&mA, result8Bit);
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}
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void Cpu65816::execute16BitADC(OpCode &opCode) {
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Address dataAddress = getAddressOfOpCodeData(opCode);
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uint16_t value = mSystemBus.readTwoBytes(dataAddress);
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uint16_t accumulator = mA;
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uint16_t carryValue = mCpuStatus.carryFlag() ? 1 : 0;
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uint32_t result32Bit = accumulator + value + carryValue;
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// Is there a carry out of the penultimate bit, redo the sum with 15 bits value and find out.
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accumulator &= 0x7FFF;
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value &= 0x7FFF;
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uint16_t partialResult = accumulator + value + carryValue;
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// Is bit 8 set?
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bool carryOutOfPenultimateBit = partialResult & 0x8000;
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// Is there a carry out of the last bit, check bit 16 for that
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bool carryOutOfLastBit = result32Bit & 0x010000;
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bool overflow = carryOutOfLastBit ^ carryOutOfPenultimateBit;
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if (overflow) mCpuStatus.setOverflowFlag();
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else mCpuStatus.clearOverflowFlag();
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if (carryOutOfLastBit) mCpuStatus.setCarryFlag();
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else mCpuStatus.clearCarryFlag();
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uint8_t result16Bit = Binary::lower16BitsOf(result32Bit);
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// Update sign and zero flags
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mCpuStatus.updateSignAndZeroFlagFrom8BitValue(result16Bit);
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// Store the 16 bit result in the accumulator
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mA = result16Bit;
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}
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void Cpu65816::execute8BitBCDADC(OpCode &opCode) {
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Address dataAddress = getAddressOfOpCodeData(opCode);
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uint8_t value = mSystemBus.readByte(dataAddress);
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uint8_t accumulator = Binary::lower8BitsOf(mA);
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uint8_t result = 0;
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bool carry = Binary::bcdSum8Bit(value, accumulator, &result, mCpuStatus.carryFlag());
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if (carry) mCpuStatus.setCarryFlag();
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else mCpuStatus.clearCarryFlag();
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Binary::setLower8BitsOf16BitsValue(&mA, result);
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mCpuStatus.updateSignAndZeroFlagFrom8BitValue(result);
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}
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void Cpu65816::execute16BitBCDADC(OpCode &opCode) {
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Address dataAddress = getAddressOfOpCodeData(opCode);
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uint16_t value = mSystemBus.readTwoBytes(dataAddress);
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uint16_t accumulator = mA;
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uint16_t result = 0;
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bool carry = Binary::bcdSum16Bit(value, accumulator, &result, mCpuStatus.carryFlag());
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if (carry) mCpuStatus.setCarryFlag();
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else mCpuStatus.clearCarryFlag();
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mA = result;
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mCpuStatus.updateSignAndZeroFlagFrom8BitValue(result);
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}
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void Cpu65816::executeADC(OpCode &opCode) {
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if (accumulatorIs8BitWide()) {
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if (mCpuStatus.decimalFlag()) execute8BitBCDADC(opCode);
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else execute8BitADC(opCode);
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} else {
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if (mCpuStatus.decimalFlag()) execute16BitBCDADC(opCode);
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else execute16BitADC(opCode);
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addToCycles(1);
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}
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// All OpCodes take one more cycle on 65C02 in decimal mode
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#ifdef EMU_65C02
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if (mCpuStatus.decimalFlag()) {
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addToCycles(1);
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}
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#endif
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switch (opCode.getCode()) {
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switch (opCode.getCode()) {
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case (0x69): // ADC Immediate
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{
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if (accumulatorIs16BitWide()) {
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addToProgramAddress(1);
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}
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addToProgramAddress(2);
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addToCycles(2);
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break;
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}
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case (0x6D): // ADC Absolute
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{
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addToProgramAddress(3);
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addToCycles(4);
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break;
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}
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case (0x6F): // ADC Absolute Long
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{
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addToProgramAddress(4);
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addToCycles(5);
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break;
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}
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case (0x65): // ADC Direct Page
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(3);
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break;
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}
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case (0x72): // ADC Direct Page Indirect
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(5);
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break;
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}
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case (0x67): // ADC Direct Page Indirect Long
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(6);
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break;
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}
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case (0x7D): // ADC Absolute Indexed, X
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{
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if (opCodeAddressingCrossesPageBoundary(opCode)) {
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addToCycles(1);
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}
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addToProgramAddress(3);
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addToCycles(4);
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break;
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}
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case (0x7F): // ADC Absolute Long Indexed, X
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{
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addToProgramAddress(4);
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addToCycles(5);
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break;
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}
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case (0x79): // ADC Absolute Indexed Y
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{
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if (opCodeAddressingCrossesPageBoundary(opCode)) {
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addToCycles(1);
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}
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addToProgramAddress(3);
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addToCycles(4);
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break;
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}
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case (0x75): // ADC Direct Page Indexed, X
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(4);
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break;
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}
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case (0x61): // ADC Direct Page Indexed Indirect, X
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(6);
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break;
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}
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case (0x71): // ADC Direct Page Indirect Indexed, Y
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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if (opCodeAddressingCrossesPageBoundary(opCode)) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(5);
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break;
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}
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case (0x77): // ADC Direct Page Indirect Long Indexed, Y
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{
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if (Binary::lower8BitsOf(mD) != 0) {
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addToCycles(1);
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}
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addToProgramAddress(2);
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addToCycles(6);
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break;
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}
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case (0x63): // ADC Stack Relative
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{
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addToProgramAddress(2);
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addToCycles(4);
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break;
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}
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case (0x73): // ADC Stack Relative Indirect Indexed, Y
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{
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addToProgramAddress(2);
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addToCycles(7);
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break;
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}
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default: {
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LOG_UNEXPECTED_OPCODE(opCode);
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}
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}
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}
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}
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