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//
// Copyright (c) 2012 Ian Cowburn
//
using System;
namespace Noddybox.Emulation.EightBit.Z80
{
/// <summary>
/// Provides an implementation of a Zilog Z80 processor.
/// </summary>
public partial class Z80Cpu : ICpu
{
#region Private types
[Flags]
private enum Z80Flags
{
None = 0x00,
Carry = 0x01,
Neg = 0x02,
PV = 0x04,
Hidden3 = 0x08,
HalfCarry = 0x10,
Hidden5 = 0x20,
Zero = 0x40,
Sign = 0x80,
Hidden = Hidden3 | Hidden5
};
#endregion
#region Private data
// Lookup tables
//
private Z80Flags[] PSZtable = new Z80Flags[512];
private Z80Flags[] SZtable = new Z80Flags[512];
private Z80Flags[] Ptable = new Z80Flags[512];
private Z80Flags[] Stable = new Z80Flags[512];
private Z80Flags[] Ztable = new Z80Flags[512];
private Z80Flags[] H35table = new Z80Flags[512];
// Machine accessors
//
private IMemory memory;
private IDevice device;
private Clock clock;
// Main registers
//
private byte A;
private Z80Flags F;
private Register16 BC = new Register16(0);
private Register16 DE = new Register16(0);
private Register16 HL = new Register16(0);
private Register16 IX = new Register16(0);
private Register16 IY = new Register16(0);
private ushort SP;
private ushort PC;
// Alternate registers
//
private Register16 AF_ = new Register16(0);
private Register16 BC_ = new Register16(0);
private Register16 DE_ = new Register16(0);
private Register16 HL_ = new Register16(0);
// Auxilliary registers and flags
//
private byte I;
private byte R;
private bool IFF1;
private bool IFF2;
private int IM;
private bool HALT;
private int shift;
#endregion
#region ICpu Members
public void Initialise(IMemory memory, IDevice device, Clock clock)
{
this.memory = memory;
this.device = device;
this.clock = clock;
Reset();
}
public void Reset()
{
PC = 0;
A = 0xff;
F = (Z80Flags)0xff;
BC.reg = 0xffff;
DE.reg = 0xffff;
HL.reg = 0xffff;
AF_.reg = 0xffff;
BC_.reg = 0xffff;
DE_.reg = 0xffff;
HL_.reg = 0xffff;
IX.reg = 0xffff;
IY.reg = 0xffff;
SP = 0xffff;
IFF1 = false;
IFF2 = false;
IM = 0;
I = 0;
R = 0;
HALT = false;
shift = 0;
}
public void Step()
{
// TODO: Single step.
}
public void Run()
{
while(!clock.FrameDone)
{
Step();
}
}
public void MaskableInterrupt(byte value)
{
clock.Add(2);
// TODO: INT
}
public void NonMaskableInterrupt(byte value)
{
clock.Add(2);
// TODO: NMI
}
#endregion
#region Constructors
public Z80Cpu()
{
// Verify runtime
//
Register16.Verify();
// Setup lookup tables
//
for(int f = 0; f < 256; f++)
{
Z80Flags p = Z80Flags.None;
Z80Flags z = Z80Flags.None;
Z80Flags s = Z80Flags.None;
Z80Flags h3 = Z80Flags.None;
Z80Flags h5 = Z80Flags.None;
int parity = 0;
for(int b=0; b < 8; b++)
{
if ((f & (1<<b)) == (1<<b))
{
parity++;
}
}
if ((parity & 1) == 1)
{
p = Z80Flags.PV;
}
if (f == 0)
{
z = Z80Flags.Zero;
}
if ((f & 0x80) == 0x80)
{
s = Z80Flags.Sign;
}
if ((f & (int)Z80Flags.Hidden3) == (int)Z80Flags.Hidden3)
{
h3 = Z80Flags.Hidden3;
}
if ((f & (int)Z80Flags.Hidden5) == (int)Z80Flags.Hidden5)
{
h5 = Z80Flags.Hidden5;
}
Ptable[f] = p;
Stable[f] = s;
Ztable[f] = z;
SZtable[f] =z | s;
PSZtable[f] = z | s | p;
H35table[f] = h3 | h5;
Ptable[f+256] = Ptable[f] | Z80Flags.Carry;
Stable[f+256] = Stable[f] | Z80Flags.Carry;
Ztable[f+256] = Ztable[f] | Z80Flags.Carry;
SZtable[f+256] = SZtable[f] | Z80Flags.Carry;
PSZtable[f+256] = PSZtable[f] | Z80Flags.Carry;
H35table[f+256] = h3 | h5;
}
Reset();
}
#endregion
}
}
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