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

using System;
using System.Linq;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Collections.Generic;
using BizHawk.Emulation.CPUs.M6502;

namespace BizHawk.Emulation.Consoles.Nintendo
{
	public partial class NES : IEmulator
	{
		//hardware/state
		protected MOS6502 cpu;
		int cpu_accumulate; //cpu timekeeper
		public PPU ppu;
		byte[] ram;
		protected byte[] CIRAM; //AKA nametables
		string game_name; //friendly name exposed to user and used as filename base
		CartInfo cart; //the current cart prototype. should be moved into the board, perhaps
		INESBoard board; //the board hardware that is currently driving things

		//user configuration 
		int[,] palette; //TBD!!
		IPortDevice[] ports;

		public void HardReset()
		{
			cpu = new MOS6502();
			cpu.ReadMemory = ReadMemory;
			cpu.WriteMemory = WriteMemory;
			ppu = new PPU(this);
			ram = new byte[0x800];
			CIRAM = new byte[0x800];
			ports = new IPortDevice[2];
			ports[0] = new JoypadPortDevice(this);
			ports[1] = new NullPortDevice();

			//fceux uses this technique, which presumably tricks some games into thinking the memory is randomized
			for (int i = 0; i < 0x800; i++)
			{
				if ((i & 4) != 0) ram[i] = 0xFF; else ram[i] = 0x00;
			}

			//in this emulator, reset takes place instantaneously
			cpu.PC = (ushort)(ReadMemory(0xFFFC) | (ReadMemory(0xFFFD) << 8));

			//cpu.debug = true;
		}

		public void FrameAdvance(bool render)
		{
			Controller.UpdateControls(Frame++);
			ppu.FrameAdvance();
		}

		protected void RunCpu(int cycles)
		{
			if (ppu.PAL)
				cycles *= 15;
			else
				cycles *= 16;

			cpu_accumulate += cycles;
			int todo = cpu_accumulate / 48;
			cpu_accumulate -= todo * 48;
			if (todo > 0)
				cpu.Execute(todo);
		}

		public byte ReadPPUReg(int addr)
		{
			return ppu.ReadReg(addr);
		}

		public byte ReadReg(int addr)
		{
			switch (addr)
			{
				case 0x4016:
				case 0x4017:
					return read_joyport(addr);
				default:
					//Console.WriteLine("read register: {0:x4}", addr);
					break;

			}
			return 0xFF;
		}

		void WritePPUReg(int addr, byte val)
		{
			ppu.WriteReg(addr, val);
		}

		void WriteReg(int addr, byte val)
		{
			switch (addr)
			{
				case 0x4014: Exec_OAMDma(val); break;
				case 0x4016:
					ports[0].Write(val & 1);
					ports[1].Write(val & 1);
					break;
				default:
					//Console.WriteLine("wrote register: {0:x4} = {1:x2}", addr, val);
					break;
			}
		}

		byte read_joyport(int addr)
		{
			//read joystick port
			//many todos here
			if (addr == 0x4016)
			{
				byte ret = ports[0].Read();
				return ret;
			}
			else return 0;
		}

		void Exec_OAMDma(byte val)
		{
			ushort addr = (ushort)(val << 8);
			for (int i = 0; i < 256; i++)
			{
				byte db = ReadMemory((ushort)addr);
				WriteMemory(0x2004, db);
				addr++;
			}
			cpu.PendingCycles -= 512;
		}

		public byte ReadMemory(ushort addr)
		{
			if (addr < 0x0800) return ram[addr];
			else if (addr < 0x1000) return ram[addr - 0x0800];
			else if (addr < 0x1800) return ram[addr - 0x1000];
			else if (addr < 0x2000) return ram[addr - 0x1800];
			else if (addr < 0x4000) return ReadPPUReg(addr & 7);
			else if (addr < 0x4020) return ReadReg(addr); //we're not rebasing the register just to keep register names canonical
			else if (addr < 0x6000) return 0xFF; //exp rom
			else if (addr < 0x8000) return board.ReadPRAM(addr);
			else return board.ReadPRG(addr - 0x8000);
		}

		public void WriteMemory(ushort addr, byte value)
		{
			if (addr < 0x0800) ram[addr] = value;
			else if (addr < 0x1000) ram[addr - 0x0800] = value;
			else if (addr < 0x1800) ram[addr - 0x1000] = value;
			else if (addr < 0x2000) ram[addr - 0x1800] = value;
			else if (addr < 0x4000) WritePPUReg(addr & 7, value);
			else if (addr < 0x4020) WriteReg(addr, value);  //we're not rebasing the register just to keep register names canonical
			else if (addr < 0x6000) { } //exp rom
			else if (addr < 0x8000) board.WritePRAM(addr, value);
			else board.WritePRG(addr - 0x8000, value);
		}

	}
}