nes: mapper "TENGEN-800008". support Tetris (Tengen)

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -323,6 +323,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Taito_X1_005.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Taito_X1_017.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\TENGEN-800032.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\TENGEN_800008.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\UxROM.cs">
       <SubType>Code</SubType>
     </Compile>

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/TENGEN_800008.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	// tetris (unl)
+	// behaves identically to CNROM for the one board it is on, but supports more (64K prg, 64K chr)
+	// http://kevtris.org/mappers/tengen/800008.html
+	public class TENGEN_800008: NES.NESBoardBase
+	{
+		int prg_mask;
+		int chr_mask;
+		int prg;
+		int chr;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "TENGEN-800008":
+					AssertPrg(32, 64);
+					AssertChr(8, 16, 32, 64);
+					AssertWram(0);
+					AssertVram(0);
+					break;
+				default:
+					return false;
+			}
+
+			prg_mask = (Cart.prg_size / 32) - 1;
+			chr_mask = (Cart.chr_size / 8) - 1;
+
+			return true;
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			value = HandleNormalPRGConflict(addr, value);
+			prg = value >> 3 & prg_mask;
+			chr = value & chr_mask;
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			return ROM[addr | prg << 15];
+		}
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+				return VROM[addr | chr << 13];
+			else
+				return base.ReadPPU(addr);
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("prg", ref prg);
+			ser.Sync("chr", ref chr);
+		}
+	}
+}