public int Process(ICpu cpu, byte instruction)
{
var ins = Instructions.Get(instruction);
if (ins is null)
{
throw new UnknownInstructionException(instruction);
}
var(mode, insType, cycles) = ins.OpCodes[instruction];
var addrMode = AddressingModes.Get(mode);
var(address, pageCrossed) = addrMode.Addressing(cpu.CpuRegisters, cpu.Bus);
var extraCycles = ins.Invoke(cpu, instruction, address);
var cyclesIncrement = insType switch
{
InstructionType.Common => extraCycles,
InstructionType.CrossingPage => InstructionUtil.GetCrossingPageClockCycles(pageCrossed) + extraCycles,
InstructionType.Branch => InstructionUtil.GetBranchClockCycle(Convert.ToBoolean(extraCycles),
pageCrossed),
_ => extraCycles
};
return(cycles + cyclesIncrement);
}
}
public static byte ReadData(this IInstruction ins, ushort address, ICpu cpu, byte instruction)
{
if (!ins.OpCodes.TryGetValue(instruction, out var value))
{
throw new UnknownInstructionException(instruction);
}
var addressingMode = AddressingModes.Get(value.mode);
if (addressingMode.AddressingType == AddressingType.Address)
{
return(cpu.Bus.ReadByte(address));
}
return((byte)address);
}
public static void WriteData(this IInstruction ins, ushort address, byte data, ICpu cpu, byte instruction)
{
if (!ins.OpCodes.TryGetValue(instruction, out var value))
{
throw new UnknownInstructionException(instruction);
}
var addressingMode = AddressingModes.Get(value.mode);
if (value.mode == AddressingMode.AccumulatorAddressingMode)
{
cpu.CpuRegisters.A = data;
return;
}
if (addressingMode.AddressingType == AddressingType.Address)
{
cpu.Bus.WriteByte(address, data);
}
}