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https://github.com/libretro/Mesen.git
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122 lines
2.7 KiB
C++
122 lines
2.7 KiB
C++
#pragma once
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#include "stdafx.h"
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#include "BaseMapper.h"
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#include "PPU.h"
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class Nanjing : public BaseMapper
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{
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private:
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uint8_t _registers[5];
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bool _toggle;
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bool _autoSwitchCHR;
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void UpdateState()
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{
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uint8_t prgPage = _registers[0] & 0x0F | ((_registers[2] & 0x0F) << 4);
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_autoSwitchCHR = (_registers[0] & 0x80) == 0x80;
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SelectPRGPage(0, prgPage);
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}
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protected:
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virtual uint32_t GetPRGPageSize() { return 0x8000; }
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virtual uint32_t GetCHRPageSize() { return 0x1000; }
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virtual void StreamState(bool saving)
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{
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BaseMapper::StreamState(saving);
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StreamArray<uint8_t>(_registers, 5);
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Stream<bool>(_toggle);
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Stream<bool>(_autoSwitchCHR);
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}
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void InitMapper()
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{
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memset(_registers, 0, sizeof(_registers));
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_autoSwitchCHR = false;
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//"Initial value of this register is 1, initial value of "trigger" is 0."
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_toggle = false;
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_registers[4] = 1;
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SelectPRGPage(0, 0);
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SelectCHRPage(0, 0);
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SelectCHRPage(1, 0);
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}
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uint16_t RegisterStartAddress() { return 0x5000; }
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uint16_t RegisterEndAddress() { return 0x5FFF; }
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void WriteRegister(uint16_t addr, uint8_t value)
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{
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if(addr >= 0x5000 && addr <= 0x5FFF) {
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//"(Address is masked with 0x7300, except for 5101)"
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if(addr == 0x5101) {
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if(_registers[4] != 0 && value == 0) {
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//"If the value of this register is changed from nonzero to zero, "trigger" is toggled (XORed with 1)"
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_toggle = !_toggle;
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}
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_registers[4] = value;
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} else {
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switch(addr & 0x7300) {
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case 0x5000:
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_registers[0] = value;
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if(!(_registers[0] & 0x80) && PPU::GetCurrentScanline() < 128) {
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SelectCHRPage(0, 0);
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SelectCHRPage(1, 1);
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}
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UpdateState();
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break;
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case 0x5100:
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_registers[1] = value;
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if(value == 6) {
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SelectPRGPage(0, 3);
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}
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break;
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case 0x5200:
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_registers[2] = value;
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UpdateState();
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break;
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case 0x5300: _registers[3] = value; break;
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}
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}
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}
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}
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public:
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uint8_t ReadRAM(uint16_t addr)
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{
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if(addr >= 0x5000 && addr <= 0x5FFF) {
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//"Reading: (Address is masked with 0x7700)"
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switch(addr & 0x7700) {
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case 0x5100:
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//"5100 = Returns value of 5300"
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return _registers[3];
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case 0x5500:
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//"5500 = If "trigger" is 1, returns value of 5300, otherwise returns 0 "
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if(_toggle) {
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return _registers[3];
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}
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break;
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}
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return 0;
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} else {
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return BaseMapper::ReadRAM(addr);
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}
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}
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virtual void NotifyVRAMAddressChange(uint16_t addr)
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{
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if(_autoSwitchCHR) {
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if(PPU::GetCurrentScanline() == 239) {
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SelectCHRPage(0, 0);
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SelectCHRPage(1, 0);
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} else if(PPU::GetCurrentScanline() == 127) {
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SelectCHRPage(0, 1);
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SelectCHRPage(1, 1);
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}
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}
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}
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}; |