161 lines
3.5 KiB
C#
161 lines
3.5 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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namespace BizHawk.Emulation.Consoles.Nintendo
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{
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class Mapper91 : NES.NESBoardBase
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{
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/*
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* Here are Disch's original notes:
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========================
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= Mapper 091 =
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========================
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Example Game:
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--------------------------
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Street Fighter 3
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Notes:
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---------------------------
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Regs exist at $6000-7FFF, so this mapper has no SRAM.
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Registers:
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---------------------------
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Range,Mask: $6000-7FFF, $7003
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$6000-6003: CHR Regs
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$7000-7001: [.... PPPP] PRG Regs
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$7002 [.... ....] IRQ Stop
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$7003 [.... ....] IRQ Start
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CHR Setup:
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---------------------------
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$0000 $0400 $0800 $0C00 $1000 $1400 $1800 $1C00
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+---------------+---------------+---------------+---------------+
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| $6000 | $6001 | $6002 | $6003 |
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+---------------+---------------+---------------+---------------+
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PRG Setup:
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---------------------------
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$8000 $A000 $C000 $E000
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+-------+-------+-------+-------+
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| $7000 | $7001 | { -2} | { -1} |
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+-------+-------+-------+-------+
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IRQs:
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---------------------------
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IRQs on this mapper seem to behave exactly like MMC3 -- except it's fixed so that it will only fire after 8
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scanlines. This is easily emulatable by using MMC3 logic.
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Write to $7002/$7003 can translate directly to write(s) to the following MMC3 registers:
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on $7002 write:
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a) write to $E000
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on $7003 write:
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a) write $07 to $C000
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b) write to $C001
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c) write to $E001
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For details on MMC3 IRQ operation, see mapper 004
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*/
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ByteBuffer chr_regs_2k = new ByteBuffer(4);
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ByteBuffer prg_regs_8k = new ByteBuffer(4);
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int chr_bank_mask_2k, prg_bank_mask_8k;
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public override bool Configure(NES.EDetectionOrigin origin)
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{
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switch (Cart.board_type)
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{
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case "MAPPER091":
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case "MAPPER197": //GoodNES reports 197 instead of 91
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break;
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default:
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return false;
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}
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chr_bank_mask_2k = Cart.chr_size / 2 - 1;
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prg_bank_mask_8k = Cart.prg_size / 8 - 1;
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prg_regs_8k[3] = 0xFF;
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prg_regs_8k[2] = 0xFE;
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return true;
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}
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public override void Dispose()
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{
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prg_regs_8k.Dispose();
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chr_regs_2k.Dispose();
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base.Dispose();
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}
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public override void SyncState(Serializer ser)
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{
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ser.Sync("prg_regs", ref prg_regs_8k);
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ser.Sync("chr_regs", ref chr_regs_2k);
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base.SyncState(ser);
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}
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public override void WriteWRAM(int addr, byte value)
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{
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switch (addr)
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{
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case 0x0000:
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chr_regs_2k[0] = value;
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break;
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case 0x0001:
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chr_regs_2k[1] = value;
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break;
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case 0x0002:
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chr_regs_2k[2] = value;
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break;
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case 0x0003:
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chr_regs_2k[3] = value;
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break;
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case 0x1000:
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prg_regs_8k[0] = (byte)(value & 0x0F);
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break;
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case 0x1001:
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prg_regs_8k[1] = (byte)(value & 0x0F);
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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 bank_2k = (addr >> 11) - 1;
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bank_2k = chr_regs_2k[bank_2k];
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bank_2k &= chr_bank_mask_2k;
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return VROM[(bank_2k * 0x800) + addr];
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}
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return base.ReadPPU(addr);
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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 = addr >> 13;
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bank_8k = prg_regs_8k[bank_8k];
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bank_8k &= prg_bank_mask_8k;
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return ROM[(bank_8k * 0x2000) + (addr & 0x1FFF)];
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}
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}
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}
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