176 lines
3.8 KiB
C#
176 lines
3.8 KiB
C#
using BizHawk.Common;
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using BizHawk.Common.NumberExtensions;
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namespace BizHawk.Emulation.Cores.Nintendo.NES
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{
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// Adapted from FCEUX src
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internal sealed class Mapper183 : NesBoardBase
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{
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private byte[] prg = new byte[4];
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private byte[] chr = new byte[8];
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private int IRQLatch = 0;
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private int IRQCount = 0;
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private bool IRQMode;
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private bool IRQa = false;
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private bool IRQr = false;
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private int prg_bank_mask_8k, chr_bank_mask_1k, IRQPre=341;
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public override bool Configure(EDetectionOrigin origin)
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{
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switch (Cart.BoardType)
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{
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case "MAPPER183":
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break;
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default:
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return false;
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}
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prg_bank_mask_8k = Cart.PrgSize / 8 - 1;
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chr_bank_mask_1k = Cart.ChrSize - 1;
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return true;
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}
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public override void SyncState(Serializer ser)
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{
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base.SyncState(ser);
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ser.Sync(nameof(prg), ref prg, false);
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ser.Sync(nameof(chr), ref chr, false);
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}
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private void SetMirroring(int mirr)
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{
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switch (mirr & 3)
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{
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case 0: SetMirrorType(EMirrorType.Vertical); break;
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case 1: SetMirrorType(EMirrorType.Horizontal); break;
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case 2: SetMirrorType(EMirrorType.OneScreenA); break;
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case 3: SetMirrorType(EMirrorType.OneScreenB); break;
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}
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}
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public override void ClockCpu()
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{
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if (IRQa)
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{
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if (IRQMode)
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{
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IRQCount++;
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if (IRQCount == 0xFF)
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{
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IrqSignal = true;
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IRQCount = IRQLatch;
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}
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}
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else
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{
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IRQPre -= 3;
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if (IRQPre <= 0)
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{
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IRQPre += 341;
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IRQCount++;
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if (IRQCount >= 0x100)
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{
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IrqSignal = IRQa;
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IRQCount = IRQLatch;
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}
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}
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}
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}
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}
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public override void WriteWram(int addr, byte value)
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{
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WriteReg(addr + 0x6000, value);
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}
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public override void WritePrg(int addr, byte value)
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{
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WriteReg(addr + 0x8000, value);
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}
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private void WriteReg(int addr, byte value)
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{
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if ((addr & 0xF800) == 0x6800)
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{
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prg[3] = (byte)(addr & 0x3F);
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}
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else if ((addr & 0xF80C) >= 0xB000 && (addr & 0xF80C) <= 0xE00C)
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{
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int index = (((addr >> 11) - 6) | (addr >> 3)) & 7;
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chr[index] = (byte)((chr[index] & (0xF0 >> (addr & 4))) | ((value & 0x0F) << (addr & 4)));
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}
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else switch (addr & 0xF80C)
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{
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case 0x8800: prg[0] = value; break;
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case 0xA800: prg[1] = value; break;
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case 0xA000: prg[2] = value; break;
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case 0x9800: SetMirroring(value & 3); break;
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// TODO: IRQ
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case 0xF000: IRQLatch = ((IRQLatch & 0xF0) | (value & 0xF)); break;
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case 0xF004: IRQLatch = ((IRQLatch & 0x0F) | ((value & 0xF) << 4)); break;
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case 0xF008:
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IRQMode = value.Bit(2);
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IRQa = value.Bit(1);//value>0 ? true:false;
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IRQr = value.Bit(0);
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if (IRQa)
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{
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IRQPre = 341;
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IRQCount = IRQLatch;
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}
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IrqSignal = false;
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break;
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case 0xF00C:
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IrqSignal = false;
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IRQa = IRQr;
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break;
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}
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}
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public override byte ReadPpu(int addr)
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{
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if (addr < 0x2000)
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{
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int x = (addr >> 10) & 7;
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int bank = (chr[x] & chr_bank_mask_1k) << 10;
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return Vrom[bank + (addr & 0x3FF)]; // TODO
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}
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return base.ReadPpu(addr);
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}
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public override byte ReadWram(int addr)
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{
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return Rom[(((prg[3] & prg_bank_mask_8k)) << 13) + (addr & 0x1FFF)];
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}
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public override byte ReadPrg(int addr)
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{
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int bank_8k;
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if (addr < 0x2000) // 0x8000
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{
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bank_8k = prg[0] & prg_bank_mask_8k;
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}
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else if (addr < 0x4000) // 0xA000
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{
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bank_8k = prg[1] & prg_bank_mask_8k;
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}
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else if (addr < 0x6000) // 0xC000
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{
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bank_8k = prg[2] & prg_bank_mask_8k;
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}
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else
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{
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bank_8k = prg_bank_mask_8k;
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}
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return Rom[(bank_8k << 13) + (addr & 0x1FFF)];
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}
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}
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}
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