BizHawk/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/BANDAI-FCG-1.cs

using BizHawk.Common;
using BizHawk.Common.NumberExtensions;

namespace BizHawk.Emulation.Cores.Nintendo.NES
{
	/*
	I'm breaking FCG boards into 7 main types:
	
	[1] FCG-1, FCG-2: regs at 6000:7fff.
	    FCG-3: regs at 8000:ffff.  one of the following at 6000:7fff:
	[2]   nothing 
	[3]   seeprom (1kbit)
	[4]   seeprom (2kbit)
	[5]   sram (8kbyte) (SEE SIZE NOTES BELOW)
	[6] Datach Joint ROM System: daughterboard setup (DON'T KNOW MUCH ABOUT THIS)
	[7] Non-existant zombie board: regs are at 6000:ffff and 2kbit seeprom is present

	iNES #16 refers to [7], which ends up working correctly for most [1], [2], or [4] games.
	iNES #153 refers to [5], theoretically.
	iNES #157 refers to [6], theoretically.
	iNES #159 refers to [3], theoretically.
	
	We try to emulate everything but [6] here.
	
	Size notes:
	chr regs are 8 bit wide and swap 1K at a time, for a max size of 256K chr, always rom.
	prg reg is 4 bit wide and swaps 16K at a time, for a max size of 256K prg.
	[5] is a special case; it has 8K of vram and uses some of the chr banking lines to handle 512K of prgrom.
	I have no idea what [6] does.
	Every real instance of [1], [2], [3], [4] had 128K or 256K of each of chr and prg.
	*/

	public sealed class BANDAI_FCG_1 : NES.NESBoardBase 
	{
		//configuration
		int prg_bank_mask_16k, chr_bank_mask_1k;

		bool regs_prg_enable; // can the mapper regs be written to in 8000:ffff?
		bool regs_wram_enable; // can the mapper regs be written to in 6000:7fff?
		bool jump2 = false; // are we in special mode for the JUMP2 board?

		//regenerable state
		IntBuffer prg_banks_16k = new IntBuffer(2);

		//state
		int prg_reg_16k;
		ByteBuffer regs = new ByteBuffer(8);
		bool irq_enabled;
		ushort irq_counter;
		SEEPROM eprom;

		public override void SyncState(Serializer ser)
		{
			base.SyncState(ser);
			ser.Sync("prg_reg_16k", ref prg_reg_16k);
			ser.Sync("regs", ref regs);
			ser.Sync("irq_counter", ref irq_counter);
			ser.Sync("irq_enabled", ref irq_enabled);
			if (eprom != null)
				eprom.SyncState(ser);
			SyncPRG();
		}

		public override void Dispose()
		{
			base.Dispose();
			regs.Dispose();
			prg_banks_16k.Dispose();
		}

		public override bool Configure(NES.EDetectionOrigin origin)
		{
			switch (Cart.board_type)
			{
				// see notes above that explain some of this in more detail

				case "BANDAI-FCG-1": // [1]
				case "BANDAI-FCG-2": // [1]
				case "IREM-FCG-1": // [1] (the extra glue logic is to connect the two chr roms, and doesn't affect emulation)
					AssertPrg(128, 256); AssertChr(128, 256); AssertWram(0); AssertVram(0);
					regs_prg_enable = false;
					regs_wram_enable = true;
					break;
				case "BANDAI-LZ93D50": // [2]
					AssertPrg(128, 256); AssertChr(128, 256); AssertWram(0); AssertVram(0);
					regs_prg_enable = true;
					regs_wram_enable = false;
					break;
				case "BANDAI-LZ93D50+24C01": // [3]
					AssertPrg(128, 256); AssertChr(128, 256); AssertWram(0); AssertVram(0);
					eprom = new SEEPROM(false);
					regs_prg_enable = true;
					regs_wram_enable = false;
					break;
				case "MAPPER159": // [3]
					AssertPrg(128, 256); AssertChr(128, 256);
					Cart.wram_size = 0;
					regs_prg_enable = true;
					regs_wram_enable = false;
					eprom = new SEEPROM(false);
					break;
				case "BANDAI-LZ93D50+24C02": // [4]
					AssertPrg(128, 256); AssertChr(128, 256); AssertWram(0); AssertVram(0);
					eprom = new SEEPROM(true);
					regs_prg_enable = true;
					regs_wram_enable = false;
					break;
				case "MAPPER016": // [7]
					if (Cart.prg_size > 256)
					{
						// you have two options:
						// 1) assume prg > 256 => jump2 (aka mapper 153, type [5])
						//    this will break hypothetical prg oversize hacks
						// 2) assume prg > 256 => oversize regular FCG
						//    this will break famicom 2 dumps without hash match,
						//    which are marked mapper016 usually
						goto case "MAPPER153";
					}
					AssertPrg(128, 256); AssertChr(128, 256);
					Cart.wram_size = 0;
					regs_prg_enable = true;
					regs_wram_enable = true;
					eprom = new SEEPROM(true);
					break;
				case "MAPPER153": // [5]
					AssertPrg(512);
					AssertChr(0);
					Cart.vram_size = 8;
					Cart.wram_size = 8;
					regs_prg_enable = true;
					regs_wram_enable = false;
					jump2 = true;
					break;
				case "BANDAI-JUMP2": // [5]
					AssertPrg(512);
					AssertChr(0);
					AssertVram(8);
					AssertWram(8);
					regs_prg_enable = true;
					regs_wram_enable = false;
					jump2 = true;
					break;

				default:
					return false;
			}

			prg_bank_mask_16k = (Cart.prg_size / 16) - 1;
			chr_bank_mask_1k = Cart.chr_size - 1;
			
			SetMirrorType(EMirrorType.Vertical);

			prg_reg_16k = 0;
			SyncPRG();

			return true;
		}

		void SyncPRG()
		{
			prg_banks_16k[0] = prg_reg_16k & prg_bank_mask_16k;
			prg_banks_16k[1] = 0xFF & prg_bank_mask_16k;
			if (jump2)
			{
				if (regs[0].Bit(0))
				{
					prg_banks_16k[0] |= 0x10;
					prg_banks_16k[1] |= 0x10;
				}
				else // wouldn't need this, except we aren't &=15 on the prg bank addresses
				{
					prg_banks_16k[0] &= 0x0f;
					prg_banks_16k[1] &= 0x0f;
				}
			}			
		}

		void WriteReg(int reg, byte value)
		{
			//Console.WriteLine("reg {0:X2} = {1:X2}", reg, value);
			switch (reg)
			{
				case 0:
				case 1:
				case 2:
				case 3:
				case 4:
				case 5:
				case 6:
				case 7:
					regs[reg] = value;
					if (jump2) // in jump2, chr regs are rewired to swap prg
						SyncPRG();
					break;
				case 8:
					//NES.LogLine("mapping PRG {0}", value);
					prg_reg_16k = value;
					SyncPRG();
					break;
				case 9:
					switch (value & 3)
					{
						case 0: SetMirrorType(NES.NESBoardBase.EMirrorType.Vertical); break;
						case 1: SetMirrorType(NES.NESBoardBase.EMirrorType.Horizontal); break;
						case 2: SetMirrorType(NES.NESBoardBase.EMirrorType.OneScreenA); break;
						case 3: SetMirrorType(NES.NESBoardBase.EMirrorType.OneScreenB); break;
					}
					break;
				case 0xA:
					irq_enabled = value.Bit(0);
					// all write acknolwedge
					IRQSignal = false;
					break;
				case 0xB:
					irq_counter &= 0xFF00;
					irq_counter |= value;
					break;
				case 0xC:
					irq_counter &= 0x00FF;
					irq_counter |= (ushort)(value << 8);
					break;
				case 0xD:
					if (eprom != null)
						eprom.WriteByte(value);
					break;
			}
		}

		public override void WriteWRAM(int addr, byte value)
		{
			//NES.LogLine("writewram {0:X4} = {1:X2}", addr, value);
			if (regs_wram_enable)
			{
				addr &= 0xF;
				WriteReg(addr, value);
			}
			else if (jump2)
			{
				WRAM[addr] = value;
			}
		}
		public override void WritePRG(int addr, byte value)
		{
			//NES.LogLine("writeprg {0:X4} = {1:X2}", addr, value);
			if (regs_prg_enable)
			{
				addr &= 0xF;
				WriteReg(addr, value);
			}
		}

		public override byte ReadWRAM(int addr)
		{
			// reading any addr in 6000:7fff returns a single bit from the eeprom
			// in bit 4.
			if (!jump2)
			{
				byte ret = (byte)(NES.DB & 0xef);
				if (eprom != null && eprom.ReadBit(NES.DB.Bit(4)))
					ret |= 0x10;
				return ret;
			}
			else
			{
				return WRAM[addr];
			}
		}

		public override void ClockCPU()
		{
			if (irq_enabled)
			{
				irq_counter--;
				if (irq_counter == 0x0000)
				{
					IRQSignal = true;
				}
			}
		}


		public override byte ReadPRG(int addr)
		{
			int bank_16k = addr >> 14;
			int ofs = addr & ((1 << 14) - 1);
			bank_16k = prg_banks_16k[bank_16k];
			addr = (bank_16k << 14) | ofs;
			return ROM[addr];
		}

		int CalcPPUAddress(int addr)
		{
			int bank_1k = addr >> 10;
			int ofs = addr & ((1 << 10) - 1);
			bank_1k = regs[bank_1k];
			bank_1k &= chr_bank_mask_1k;
			return (bank_1k << 10) | ofs;
		}

		public override byte ReadPPU(int addr)
		{
			if (addr < 0x2000)
			{
				if (jump2)
					return VRAM[addr];
				else
					return VROM[CalcPPUAddress(addr)];
			}
			else
			{
				return base.ReadPPU(addr);
			}
		}

		public override void WritePPU(int addr, byte value)
		{
			if (addr < 0x2000)
			{
				if (jump2)
					VRAM[addr] = value;
			}
			else
			{
				base.WritePPU(addr, value);
			}
		}

		public override byte[] SaveRam
		{
			get
			{
				if (eprom != null)
					return eprom.GetSaveRAM();
				else if (jump2)
				{
					return WRAM;
				}
				else
				{
					return null;
				}
			}
		}
	}
}