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