[NES] the other 50% of mmc3. now things will mostly work

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

@@ -8,8 +8,10 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 	{
 		class MMC3 : IDisposable
 		{
+			NES.NESBoardBase board;
 			public MMC3(NES.NESBoardBase board, int num_prg_banks)
 			{
+				this.board = board;
 				bank_regs[8] = (byte)(num_prg_banks - 1);
 				bank_regs[9] = (byte)(num_prg_banks - 2);
 			}
@@ -23,11 +25,19 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			//state
 			int chr_mode, prg_mode, reg_addr;
 			public NES.NESBoardBase.EMirrorType mirror;
+			int ppubus_state, ppubus_statecounter;
 
 			//this contains the 8 programmable regs and 2 more at the end to represent PRG banks -2 and -1; and 4 more at the end to break down chr regs 0 and 1
 			ByteBuffer bank_regs = new ByteBuffer(14);
 			ByteBuffer prg_lookup = new ByteBuffer(new byte[] { 6, 7, 9, 8, 9, 7, 6, 8 });
 			ByteBuffer chr_lookup = new ByteBuffer(new byte[] { 10, 11, 12, 13, 2, 3, 4, 5 });
+			byte irq_reload, irq_counter;
+			bool irq_pending, irq_enable;
+
+			void SyncIRQ()
+			{
+				board.NES.irq_cart = irq_pending;
+			}
 
 			public void WritePRG(int addr, byte value)
 			{
@@ -55,16 +65,19 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 						//wram enable/protect
 						break;
 					case 0x4000: //$C000
-						//IRQ reload
+						irq_reload = value;
 						break;
 					case 0x4001: //$C001
-						//IRQ clear
+						irq_counter = 0;
 						break;
 					case 0x6000: //$E000
-						//IRQ ack/disable
+						irq_enable = false;
+						irq_pending = false;
+						SyncIRQ();
 						break;
 					case 0x6001: //$E001
-						//IRQ enable
+						irq_enable = true;
+						SyncIRQ();
 						break;
 				}
 			}
@@ -85,6 +98,38 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				return bank_1k;
 			}
 
+			void ClockIRQ()
+			{
+				if(irq_counter == 0)
+					irq_counter = irq_reload;
+				else {
+					irq_counter--;
+					//Console.WriteLine(irq_counter);
+					if (irq_counter == 0)
+					{
+						if (irq_enable)
+							irq_pending = true;
+						SyncIRQ();
+					}
+				}
+			}
+
+			//TODO - this should be determined from NES timestamps to correctly emulate ppu writes interfering
+			public void Tick_PPU(int addr)
+			{
+				ppubus_statecounter++;
+				int state = (addr >> 12)&1;
+				if(ppubus_state == 0 && ppubus_statecounter > 1 && state == 1)
+				{
+					ppubus_statecounter = 0;
+					ClockIRQ();
+				}
+				if(ppubus_state != state)
+				{
+					ppubus_state = state;
+				}
+			}
+
 		}
 
 		//configuration
@@ -115,6 +160,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 		public override byte ReadPPU(int addr)
 		{
+			mmc3.Tick_PPU(addr);
 			if (addr < 0x2000)
 			{
 				int bank_1k = mmc3.Get_CHRBank_1K(addr);
@@ -129,6 +175,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 		public override void WritePPU(int addr, byte value)
 		{
+			mmc3.Tick_PPU(addr);
 			base.WritePPU(addr, value);
 		}
 

BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs

@@ -23,11 +23,12 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		CartInfo cart; //the current cart prototype. should be moved into the board, perhaps
 		INESBoard board; //the board hardware that is currently driving things
 
-		bool _irq_apu;
+		bool _irq_apu, _irq_cart;
 		public bool irq_apu { get { return _irq_apu; } set { _irq_apu = value; sync_irq(); } }
+		public bool irq_cart { get { return _irq_cart; } set { _irq_cart = value; sync_irq(); } }
 		void sync_irq()
 		{
-			cpu.IRQ = _irq_apu;
+			cpu.IRQ = _irq_apu || _irq_cart;
 		}
 
 		//user configuration 

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

@@ -433,6 +433,9 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			ser.Sync("ram", ref ram, false);
 			ser.Sync("CIRAM", ref CIRAM, false);
 			ser.Sync("cpu_accumulate", ref cpu_accumulate);
+			ser.Sync("_irq_apu", ref _irq_apu);
+			ser.Sync("_irq_cart", ref _irq_cart);
+			sync_irq();
             //string inp = GetControllersAsMnemonic();  TODO sorry bout that
             //ser.SyncFixedString("input", ref inp, 32);
 			board.SyncState(ser);

BizHawk.Emulation/Consoles/Nintendo/NES/PPU.run.cs

@@ -323,10 +323,14 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 							int patternNumber = oam->oam[1];
 							int patternAddress;
 
-							//create deterministic dummy fetch pattern
+							//create deterministic dummy fetch pattern.
 							if (oam->present==0)
 							{
-								patternNumber = 0;
+								//according to nintendulator:
+								//* On the first empty sprite slot, read the Y-coordinate of sprite #63 followed by $FF for the remaining 7 cycles
+								//* On all subsequent empty sprite slots, read $FF for all 8 reads
+								//well, we shall just read $FF and that is good enough for now to make mmc3 work
+								patternNumber = 0xFF;
 								line = 0;
 							}