Mapper 216 - supported enough for Magic Jewelry 2 to work

BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj

@@ -478,6 +478,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\BANDAI-FCG-1.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\BANDAI_74_161_02_74.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\BANDAI_74_161_161_32.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Bonza.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\BxROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Camerica.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\CoolBoy.cs" />

BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Bonza.cs

@@ -0,0 +1,64 @@
+using BizHawk.Common;
+
+namespace BizHawk.Emulation.Cores.Nintendo.NES
+{
+	// Bonza (R)
+	// Magic Jewelry 2 (Unl)
+	public class Bonza : NES.NESBoardBase
+	{
+		private int _chrReg;
+		private int _prgReg;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER216":
+					break;
+				default:
+					return false;
+			}
+
+			return true;
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("chrReg", ref _chrReg);
+			ser.Sync("prgReg", ref _prgReg);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			_prgReg = addr & 1;
+			_chrReg = (addr >> 1) & 7;
+		}
+
+		public override byte ReadEXP(int addr)
+		{
+			if (addr == 0x1000)
+			{
+				return 0;
+			}
+
+			return base.ReadEXP(addr);
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			return ROM[(_prgReg * 0x8000) + (addr & 0x7FFF)];
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			// Magic Jewelry has no VROM and does not write chr regs
+			if (addr < 0x2000 && VROM != null)
+			{
+				return VROM[(_chrReg * 2000) + (addr & 0x1FFF)];
+			}
+
+			return base.ReadPPU(addr);
+		}
+	}
+}