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CLK/Machines/Atari/2600/Cartridges/MNetwork.hpp

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//
// CartridgeMNetwork.h
// Clock Signal
//
// Created by Thomas Harte on 18/03/2017.
// Copyright 2017 Thomas Harte. All rights reserved.
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//
#ifndef Atari2600_CartridgeMNetwork_hpp
#define Atari2600_CartridgeMNetwork_hpp
#include "Cartridge.hpp"
namespace Atari2600 {
namespace Cartridge {
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class MNetwork: public BusExtender {
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public:
MNetwork(uint8_t *rom_base, std::size_t rom_size) :
BusExtender(rom_base, rom_size) {
rom_ptr_[0] = rom_base + rom_size_ - 4096;
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rom_ptr_[1] = rom_ptr_[0] + 2048;
high_ram_ptr_ = high_ram_;
}
void perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
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address &= 0x1fff;
if(!(address & 0x1000)) return;
if(address >= 0x1fe0 && address <= 0x1fe6) {
rom_ptr_[0] = rom_base_ + (address - 0x1fe0) * 2048;
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} else if(address == 0x1fe7) {
rom_ptr_[0] = nullptr;
} else if(address >= 0x1ff8 && address <= 0x1ffb) {
int offset = (address - 0x1ff8) * 256;
high_ram_ptr_ = &high_ram_[offset];
}
if(address & 0x800) {
if(address < 0x1900) {
high_ram_ptr_[address & 255] = *value;
} else if(address < 0x1a00) {
if(isReadOperation(operation)) *value = high_ram_ptr_[address & 255];
} else {
if(isReadOperation(operation)) *value = rom_ptr_[1][address & 2047];
}
} else {
if(rom_ptr_[0]) {
if(isReadOperation(operation)) *value = rom_ptr_[0][address & 2047];
} else {
if(address < 0x1400) {
low_ram_[address & 1023] = *value;
} else {
if(isReadOperation(operation)) *value = low_ram_[address & 1023];
}
}
}
}
private:
uint8_t *rom_ptr_[2];
uint8_t *high_ram_ptr_;
uint8_t low_ram_[1024], high_ram_[1024];
};
}
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}
#endif /* Atari2600_CartridgeMNetwork_hpp */