nes Mapper 42: dumb FDS conversion pirate stuff

Ai Senshi Nicol [p1].nes
Bio Miracle Bokutte Upa (J) (Mario Baby - FDS Conversion).nes

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -155,6 +155,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper027.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper038.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper040.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper042.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper045.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper057.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper058.cs" />

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper042.cs

@@ -0,0 +1,117 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	// pirate FDS conversion
+	// this is probably two different boards, but they seem to work well enough the same
+	public class Mapper042 : NES.NESBoardBase
+	{
+		int prg = 0;
+		int chr = 0;
+		int irqcnt = 0;
+		bool irqenable = false;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER042":
+					break;
+				default:
+					return false;
+			}
+			AssertPrg(128);
+
+			if (Cart.vram_size == 0)
+				AssertChr(128);
+			else
+			{
+				AssertVram(8);
+				AssertChr(0);
+			}
+
+			AssertWram(0);
+			// not sure on initial mirroring
+			SetMirrorType(EMirrorType.Vertical);
+			return true;
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			addr &= 0x6003;
+			switch (addr)
+			{
+				case 0x0000:
+					chr = value & 15;
+					break;
+				case 0x6000:
+					prg = value & 15;
+					break;
+				case 0x6001:
+					if ((value & 8) != 0)
+						SetMirrorType(EMirrorType.Horizontal);
+					else
+						SetMirrorType(EMirrorType.Vertical);
+					break;
+				case 0x6002:
+					Console.WriteLine("{0:x4}:{1:x2}  @{2}", addr + 0x8000, value, NES.ppu.ppur.status.sl);
+					if ((value & 2) == 0)
+					{
+						irqcnt = 0;
+						irqenable = false;
+						IRQSignal = false;
+					}
+					else
+						irqenable = true;
+					break;
+			}
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			return ROM[addr | 0x18000];
+		}
+		public override byte ReadWRAM(int addr)
+		{
+			return ROM[addr | prg << 13];
+		}
+
+		public override void ClockPPU()
+		{
+			if (irqenable)
+			{
+				irqcnt++;
+
+				if (irqcnt >= 32768 * 3)
+					irqcnt -= 32768 * 3;
+
+				IRQSignal = irqcnt >= 24576 * 3;
+			}
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("prg", ref prg);
+			ser.Sync("chr", ref chr);
+			ser.Sync("irqenable", ref irqenable);
+			ser.Sync("irqcnt", ref irqcnt);
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+			{
+				if (VRAM != null)
+					return VRAM[addr];
+				else
+					return VROM[addr | chr << 13];
+			}
+			else			
+				return base.ReadPPU(addr);
+		}
+	}
+}