77 lines
1.4 KiB
C
77 lines
1.4 KiB
C
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#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 Mapper42 : public BaseMapper
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{
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private:
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uint16_t _irqCounter;
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bool _irqEnabled;
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protected:
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virtual uint16_t GetPRGPageSize() { return 0x2000; }
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virtual uint16_t GetCHRPageSize() { return 0x2000; }
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void InitMapper()
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{
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_irqCounter = 0;
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_irqEnabled = false;
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SelectPRGPage(0, 0x0C);
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SelectPRGPage(1, 0x0D);
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SelectPRGPage(2, 0x0E);
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SelectPRGPage(3, 0x0F);
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SelectCHRPage(0, 0);
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}
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void StreamState(bool saving)
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{
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BaseMapper::StreamState(saving);
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Stream(_irqCounter, _irqEnabled);
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}
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void ProcessCpuClock()
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{
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if(_irqEnabled) {
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_irqCounter++;
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if(_irqCounter >= 0x8000) {
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_irqCounter -= 0x8000;
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}
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if(_irqCounter >= 0x6000) {
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CPU::SetIRQSource(IRQSource::External);
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} else {
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CPU::ClearIRQSource(IRQSource::External);
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}
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}
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}
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void WriteRegister(uint16_t addr, uint8_t value)
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{
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switch(addr & 0xE003) {
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case 0x8000:
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if(_chrRomSize > 0) {
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SelectCHRPage(0, value & 0x0F);
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}
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break;
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case 0xE000:
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SetCpuMemoryMapping(0x6000, 0x7FFF, value & 0x0F, PrgMemoryType::PrgRom);
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break;
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case 0xE001:
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SetMirroringType(value & 0x08 ? MirroringType::Horizontal : MirroringType::Vertical);
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break;
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case 0xE002:
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_irqEnabled = (value == 0x02);
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if(!_irqEnabled) {
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CPU::ClearIRQSource(IRQSource::External);
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_irqCounter = 0;
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}
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break;
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}
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}
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};
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