BizHawk/BizHawk.Emulation/Computers/Commodore64/MOS/Chip4864.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BizHawk.Emulation.Computers.Commodore64.MOS
{
	// DRAM for the c64
	// 4164 = 64 kbit
	// 4464 = 256 kbit
	// 4864 = 512 kbit
	
	// for purposes of simplification we'll just
	// use one 4864, the C64 can use sets of 4164 or
	// 4464 typically

	// memory is striped 00/FF at intervals of 0x40

	public class Chip4864 : IStandardIO
	{
		private byte[] ram;

		public Chip4864()
		{
			ram = new byte[0x10000];
			HardReset();
		}

		public void HardReset()
		{
			// stripe the ram
			for (int i = 0; i < 10000; i++)
				ram[i] = ((i & 0x40) != 0) ? (byte)0xFF : (byte)0x00;
		}

		public byte Peek(int addr)
		{
			return ram[addr & 0xFFFF];
		}

		public void Poke(int addr, byte val)
		{
			ram[addr & 0xFFFF] = val;
		}

		public byte Read(ushort addr)
		{
			return ram[addr];
		}

		public void Write(ushort addr, byte val)
		{
			ram[addr] = val;
		}
	}
}