109 lines
2.6 KiB
C#
109 lines
2.6 KiB
C#
using BizHawk.Common;
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namespace BizHawk.Emulation.Consoles.Nintendo
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{
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// RacerMate II
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// 64KB PRGROM, 64KB CHRRAM(!), CHRRAM is battry backed (!!)
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// the "ram protect" function is not emulated. the notes i found said that it
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// defaults to off, the control regs are write only, and cannot be reenabled. so...
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// todo: special controller, and IRQ is possibly wrong
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public sealed class Mapper168 : NES.NESBoardBase
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{
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int prg = 0;
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int chr = 0;
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int irqclock = 2048;
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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 "MAPPER168":
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case "UNL-RACERMATE":
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break;
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default:
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return false;
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}
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AssertPrg(64);
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Cart.chr_size = 0; //AssertChr(0); //shitty dumps
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Cart.vram_size = 64; //AssertVram(64); //shitty dumps
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AssertWram(0);
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//AssertBattery(true); // battery is handled directly
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SetMirrorType(Cart.pad_h, Cart.pad_v);
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return true;
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}
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public override byte ReadPRG(int addr)
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{
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if (addr >= 0x4000)
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return ROM[addr + 0x8000];
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else
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return ROM[addr + (prg << 14)];
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}
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// the chr reg on hardware is supposedly bitscrambled and then inverted from
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// what would be expected. since it doesn't make a difference and i don't know
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// of any clear source on what it's actually supposed to be, ignore.
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int Scramble(int chr)
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{
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return chr;
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}
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public override void WritePRG(int addr, byte value)
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{
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if (addr < 0x4000)
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{
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chr = value & 15;
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prg = value >> 6 & 3;
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}
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else if (addr == 0x7080) // ack
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IRQSignal = false;
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else if (addr == 0x7000) // start count
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irqclock = 0;
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}
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public override byte ReadPPU(int addr)
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{
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if (addr < 0x1000)
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return VRAM[addr | Scramble(0) << 12];
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else if (addr < 0x2000)
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return VRAM[(addr & 0xfff) | Scramble(chr) << 12];
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else
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return base.ReadPPU(addr);
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}
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public override void WritePPU(int addr, byte value)
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{
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if (addr < 0x1000)
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VRAM[addr | Scramble(0) << 12] = value;
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else if (addr < 0x2000)
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VRAM[(addr & 0xfff) | Scramble(chr) << 12] = value;
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else
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base.WritePPU(addr, value);
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}
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public override byte[] SaveRam { get { return VRAM; } }
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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("prg", ref prg);
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ser.Sync("chr", ref chr);
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ser.Sync("irqclock", ref irqclock);
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}
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public override void ClockCPU()
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{
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if (irqclock == 2048 - 1)
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{
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irqclock++;
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IRQSignal = true;
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}
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else if (irqclock < 2048 - 1)
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{
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irqclock++;
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}
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}
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}
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}
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