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76 lines
1.9 KiB
C++
76 lines
1.9 KiB
C++
#pragma once
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#include "stdafx.h"
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#include "BaseMapper.h"
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#include "CPU.h"
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class VRC3 : public BaseMapper
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{
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private:
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bool _irqEnableOnAck = false;
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bool _irqEnabled = false;
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bool _smallCounter = false;
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uint16_t _irqReload = 0;
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uint16_t _irqCounter = 0;
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protected:
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virtual uint16_t GetPRGPageSize() override { return 0x4000; }
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virtual uint16_t GetCHRPageSize() override { return 0x2000; }
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void InitMapper() override
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{
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SelectPRGPage(1, -1);
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SelectCHRPage(0, 0);
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}
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virtual void StreamState(bool saving) override
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{
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BaseMapper::StreamState(saving);
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Stream(_irqEnableOnAck, _smallCounter, _irqEnabled, _irqCounter, _irqReload);
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}
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virtual void ProcessCpuClock() override
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{
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if(_irqEnabled) {
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if(_smallCounter) {
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uint8_t smallCounter = _irqCounter & 0xFF;
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smallCounter++;
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if(_smallCounter == 0) {
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smallCounter = _irqReload & 0xFF;
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CPU::SetIRQSource(IRQSource::External);
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}
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_irqCounter = (_irqCounter & 0xFF00) | smallCounter;
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} else {
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_irqCounter++;
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if(_irqCounter == 0) {
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_irqCounter = _irqReload;
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CPU::SetIRQSource(IRQSource::External);
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}
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}
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}
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}
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void WriteRegister(uint16_t addr, uint8_t value) override
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{
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switch(addr & 0xF000) {
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case 0x8000: _irqReload = (_irqReload & 0xFFF0) | (value & 0x0F); break;
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case 0x9000: _irqReload = (_irqReload & 0xFF0F) | ((value & 0x0F) << 4); break;
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case 0xA000: _irqReload = (_irqReload & 0xF0FF) | ((value & 0x0F) << 8); break;
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case 0xB000: _irqReload = (_irqReload & 0x0FFF) | ((value & 0x0F) << 12); break;
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case 0xC000:
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_irqEnabled = (value & 0x02) == 0x02;
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if(_irqEnabled) {
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_irqCounter = _irqReload;
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}
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_smallCounter = (value & 0x04) == 0x04;
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_irqEnableOnAck = (value & 0x01) == 0x01;
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CPU::ClearIRQSource(IRQSource::External);
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break;
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case 0xD000:
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CPU::ClearIRQSource(IRQSource::External);
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_irqEnabled = _irqEnableOnAck;
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break;
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case 0xF000: SelectPRGPage(0, value & 0x07); break;
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}
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}
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};
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