EightBitNet/EightBit/IntelProcessor.cs

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// <copyright file="IntelProcessor.cs" company="Adrian Conlon">
// Copyright (c) Adrian Conlon. All rights reserved.
// </copyright>
namespace EightBit
{
using System;
public abstract class IntelProcessor : LittleEndianProcessor
{
private static readonly int[] HalfCarryTableAdd = new int[8] { 0, 0, 1, 0, 1, 0, 1, 1 };
private static readonly int[] HalfCarryTableSub = new int[8] { 0, 1, 1, 1, 0, 0, 0, 1 };
private readonly IntelOpCodeDecoded[] decodedOpCodes = new IntelOpCodeDecoded[0x100];
private PinLevel haltLine;
protected IntelProcessor(Bus bus)
: base(bus)
{
for (var i = 0; i < 0x100; ++i)
{
this.decodedOpCodes[i] = new IntelOpCodeDecoded((byte)i);
}
}
public event EventHandler<EventArgs> RaisingHALT;
public event EventHandler<EventArgs> RaisedHALT;
public event EventHandler<EventArgs> LoweringHALT;
public event EventHandler<EventArgs> LoweredHALT;
public Register16 SP { get; } = new Register16((ushort)Mask.Mask16);
public Register16 MEMPTR { get; } = new Register16((ushort)Mask.Mask16);
public abstract Register16 AF { get; }
public byte A { get => this.AF.High; set => this.AF.High = value; }
public byte F { get => this.AF.Low; set => this.AF.Low = value; }
public abstract Register16 BC { get; }
public byte B { get => this.BC.High; set => this.BC.High = value; }
public byte C { get => this.BC.Low; set => this.BC.Low = value; }
public abstract Register16 DE { get; }
public byte D { get => this.DE.High; set => this.DE.High = value; }
public byte E { get => this.DE.Low; set => this.DE.Low = value; }
public abstract Register16 HL { get; }
public byte H { get => this.HL.High; set => this.HL.High = value; }
public byte L { get => this.HL.Low; set => this.HL.Low = value; }
protected bool Halted => this.HALT().Lowered();
public ref PinLevel HALT() => ref this.haltLine;
public IntelOpCodeDecoded GetDecodedOpCode(byte opCode) => this.decodedOpCodes[opCode];
public override void RaisePOWER()
{
base.RaisePOWER();
this.RaiseHALT();
this.SP.Word = this.AF.Word = this.BC.Word = this.DE.Word = this.HL.Word = (ushort)Mask.Mask16;
}
public virtual void RaiseHALT()
{
this.OnRaisingHALT();
this.HALT().Raise();
this.OnRaisedHALT();
}
public virtual void LowerHALT()
{
this.OnLoweringHALT();
this.HALT().Lower();
this.OnLoweredHALT();
}
protected static int BuildHalfCarryIndex(byte before, byte value, int calculation) => ((before & 0x88) >> 1) | ((value & 0x88) >> 2) | ((calculation & 0x88) >> 3);
protected static int CalculateHalfCarryAdd(byte before, byte value, int calculation)
{
var index = BuildHalfCarryIndex(before, value, calculation);
return HalfCarryTableAdd[index & (int)Mask.Mask3];
}
protected static int CalculateHalfCarrySub(byte before, byte value, int calculation)
{
var index = BuildHalfCarryIndex(before, value, calculation);
return HalfCarryTableSub[index & (int)Mask.Mask3];
}
protected virtual void OnRaisingHALT() => this.RaisingHALT?.Invoke(this, EventArgs.Empty);
protected virtual void OnRaisedHALT() => this.RaisedHALT?.Invoke(this, EventArgs.Empty);
protected virtual void OnLoweringHALT() => this.LoweringHALT?.Invoke(this, EventArgs.Empty);
protected virtual void OnLoweredHALT() => this.LoweredHALT?.Invoke(this, EventArgs.Empty);
protected override void HandleRESET()
{
base.HandleRESET();
this.Jump(0);
}
protected sealed override void Push(byte value) => this.BusWrite(--this.SP.Word, value);
protected sealed override byte Pop() => this.BusRead(this.SP.Word++);
protected sealed override Register16 GetWord()
{
var returned = base.GetWord();
this.MEMPTR.Word = this.Bus.Address.Word;
return returned;
}
protected sealed override void SetWord(Register16 value)
{
base.SetWord(value);
this.MEMPTR.Word = this.Bus.Address.Word;
}
////
protected void Restart(byte address)
{
this.MEMPTR.Low = address;
this.MEMPTR.High = 0;
this.Call(this.MEMPTR.Word);
}
protected bool CallConditional(bool condition)
{
this.MEMPTR.Word = this.FetchWord().Word;
if (condition)
{
this.Call(this.MEMPTR.Word);
}
return condition;
}
protected bool JumpConditional(bool condition)
{
this.MEMPTR.Word = this.FetchWord().Word;
if (condition)
{
this.Jump(this.MEMPTR.Word);
}
return condition;
}
protected bool ReturnConditional(bool condition)
{
if (condition)
{
this.Return();
}
return condition;
}
protected void JumpRelative(sbyte offset)
{
this.MEMPTR.Word = (ushort)(this.PC.Word + offset);
this.Jump(this.MEMPTR.Word);
}
protected bool JumpRelativeConditional(bool condition)
{
var offset = (sbyte)this.FetchByte();
if (condition)
{
this.JumpRelative(offset);
}
return condition;
}
protected override sealed void Return()
{
base.Return();
this.MEMPTR.Word = this.PC.Word;
}
protected void Halt()
{
--this.PC.Word;
this.LowerHALT();
}
protected void Proceed()
{
++this.PC.Word;
this.RaiseHALT();
}
}
}