mirror of https://github.com/bsnes-emu/bsnes.git
74 lines
1.8 KiB
C++
74 lines
1.8 KiB
C++
auto ICD2::readIO(uint24 addr, uint8 data) -> uint8 {
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addr &= 0x40ffff;
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//LY counter
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if(addr == 0x6000) {
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uint y = min((uint8)143, GameBoy::ppu.status.ly);
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return (y & ~7) | writeBank;
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}
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//command ready port
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if(addr == 0x6002) {
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data = packetSize > 0;
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if(data) {
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for(auto n : range(16)) r7000[n] = packet[0][n];
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packetSize--;
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for(auto n : range(packetSize)) packet[n] = packet[n + 1];
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}
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return data;
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}
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//ICD2 revision
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if(addr == 0x600f) {
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return 0x21;
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}
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//command port
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if((addr & 0x40fff0) == 0x7000) {
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return r7000[addr & 15];
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}
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//VRAM port
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if(addr == 0x7800) {
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data = output[readBank * 512 + readAddress];
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readAddress = (readAddress + 1) & 511;
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return data;
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}
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return 0x00;
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}
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auto ICD2::writeIO(uint24 addr, uint8 data) -> void {
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addr &= 0xffff;
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//VRAM port
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if(addr == 0x6001) {
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readBank = data & 3;
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readAddress = 0;
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return;
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}
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//control port
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//d7: 0 = halt, 1 = reset
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//d5,d4: 0 = 1-player, 1 = 2-player, 2 = 4-player, 3 = ???
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//d1,d0: 0 = frequency divider (clock rate adjust)
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if(addr == 0x6003) {
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if((r6003 & 0x80) == 0x00 && (data & 0x80) == 0x80) {
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reset(true);
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}
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switch(data & 3) {
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case 0: frequency = cpu.frequency / 4; break; //fast (glitchy, even on real hardware)
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case 1: frequency = cpu.frequency / 5; break; //normal
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case 2: frequency = cpu.frequency / 7; break; //slow
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case 3: frequency = cpu.frequency / 9; break; //very slow
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}
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r6003 = data;
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return;
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}
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if(addr == 0x6004) { r6004 = data; return; } //joypad 1
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if(addr == 0x6005) { r6005 = data; return; } //joypad 2
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if(addr == 0x6006) { r6006 = data; return; } //joypad 3
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if(addr == 0x6007) { r6007 = data; return; } //joypad 4
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}
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