mirror of https://github.com/bsnes-emu/bsnes.git
98 lines
2.4 KiB
C++
98 lines
2.4 KiB
C++
//MMC2
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struct NES_PxROM : Board {
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enum Revision : unsigned {
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PEEOROM,
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PNROM,
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} revision;
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uint4 prg_bank;
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uint5 chr_bank[2][2];
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bool mirror;
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bool latch[2];
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uint8 prg_read(unsigned addr) {
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if(addr < 0x6000) return cpu.mdr();
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if(addr < 0x8000) return prgram.read(addr);
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unsigned bank = 0;
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switch((addr / 0x2000) & 3) {
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case 0: bank = prg_bank; break;
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case 1: bank = 0x0d; break;
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case 2: bank = 0x0e; break;
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case 3: bank = 0x0f; break;
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}
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return prgrom.read((bank * 0x2000) | (addr & 0x1fff));
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}
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void prg_write(unsigned addr, uint8 data) {
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if(addr < 0x6000) return;
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if(addr < 0x8000) return prgram.write(addr, data);
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switch(addr & 0xf000) {
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case 0xa000: prg_bank = data & 0x0f; break;
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case 0xb000: chr_bank[0][0] = data & 0x1f; break;
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case 0xc000: chr_bank[0][1] = data & 0x1f; break;
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case 0xd000: chr_bank[1][0] = data & 0x1f; break;
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case 0xe000: chr_bank[1][1] = data & 0x1f; break;
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case 0xf000: mirror = data & 0x01; break;
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}
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}
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unsigned ciram_addr(unsigned addr) const {
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switch(mirror) {
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case 0: return ((addr & 0x0400) >> 0) | (addr & 0x03ff); //vertical mirroring
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case 1: return ((addr & 0x0800) >> 1) | (addr & 0x03ff); //horizontal mirroring
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}
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}
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uint8 chr_read(unsigned addr) {
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if(addr & 0x2000) return ppu.ciram_read(ciram_addr(addr));
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bool region = addr & 0x1000;
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unsigned bank = chr_bank[region][latch[region]];
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if((addr & 0x0ff8) == 0x0fd8) latch[region] = 0;
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if((addr & 0x0ff8) == 0x0fe8) latch[region] = 1;
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return Board::chr_read((bank * 0x1000) | (addr & 0x0fff));
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}
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void chr_write(unsigned addr, uint8 data) {
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if(addr & 0x2000) return ppu.ciram_write(ciram_addr(addr), data);
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bool region = addr & 0x1000;
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unsigned bank = chr_bank[region][latch[region]];
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if((addr & 0x0ff8) == 0x0fd8) latch[region] = 0;
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if((addr & 0x0ff8) == 0x0fe8) latch[region] = 1;
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return Board::chr_write((bank * 0x1000) | (addr & 0x0fff), data);
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}
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void power() {
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}
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void reset() {
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prg_bank = 0;
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chr_bank[0][0] = 0;
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chr_bank[0][1] = 0;
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chr_bank[1][0] = 0;
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chr_bank[1][1] = 0;
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mirror = 0;
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latch[0] = 0;
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latch[1] = 0;
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}
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void serialize(serializer& s) {
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Board::serialize(s);
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s.integer(prg_bank);
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s.integer(chr_bank[0][0]);
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s.integer(chr_bank[0][1]);
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s.integer(chr_bank[1][0]);
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s.integer(chr_bank[1][1]);
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s.integer(mirror);
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s.array(latch);
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}
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NES_PxROM(Markup::Node& document) : Board(document) {
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revision = Revision::PNROM;
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}
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};
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