private void DoVisibleScanline()
{
if (_dot >= 1 && _dot <= 256)
{
var tX = (byte)(_cntTile % 32);
var tY = (byte)(_cntTile / 32 / 8);
var tileId = tY * 32 + tX;
var bX = tX / 2;
var bY = tY / 2;
var aX = bX / 2;
var aY = bY / 2;
var aId = aY * 8 + aX;
var attrShift = (bY % 2 * 2 + bX % 2) * 2;
switch (_nextTileFetchStatus)
{
case TileFetchStatus.Nametable_1:
_masterClient.Read((ushort)(_nametableBaseAddr + tileId));
_nextTileFetchStatus = TileFetchStatus.Nametable_2;
break;
case TileFetchStatus.Nametable_2:
_nametable = _masterClient.Value;
_nextTileFetchStatus = TileFetchStatus.Attribute_1;
break;
case TileFetchStatus.Attribute_1:
_masterClient.Read((ushort)(0x23C0 + aId));
_nextTileFetchStatus = TileFetchStatus.Attribute_2;
break;
case TileFetchStatus.Attribute_2:
_attribute = (byte)((_masterClient.Value & (0b11 << attrShift)) >> attrShift);
_nextTileFetchStatus = TileFetchStatus.BitmapLow_1;
break;
case TileFetchStatus.BitmapLow_1:
_masterClient.Read(GetBgPatternTableAddress());
_nextTileFetchStatus = TileFetchStatus.BitmapLow_2;
break;
case TileFetchStatus.BitmapLow_2:
_bitmapLow = _masterClient.Value;
_nextTileFetchStatus = TileFetchStatus.BitmapHigh_1;
break;
case TileFetchStatus.BitmapHigh_1:
_masterClient.Read((ushort)(GetBgPatternTableAddress() + 8));
_nextTileFetchStatus = TileFetchStatus.BitmapHigh_2;
break;
case TileFetchStatus.BitmapHigh_2:
_bitmapHigh = _masterClient.Value;
OutputPixel();
_cntTile++;
_nextTileFetchStatus = TileFetchStatus.Nametable_1;
break;
}
}
}
void IClockSink.OnTick()
{
if (_enabled)
{
_masterClient.Read(_srcAddr++);
_masterClient.Write(0x2014);
_writeCount++;
if (_writeCount == 0)
{
_enabled = false;
_masterClient.Release();
}
}
}
private void DispatchAddressing()
{
void ReadSource(AddressOperand addressOperand, ref byte result)
{
switch (addressOperand)
{
// In Result
case AddressOperand.None:
break;
case AddressOperand.Memory:
if (_addressState.Destination != AddressOperand.PC)
{
_masterClient.Read(_addressState.MemoryAddress);
result = _masterClient.Value;
}
break;
case AddressOperand.X:
result = Registers.X;
break;
case AddressOperand.Y:
result = Registers.Y;
break;
case AddressOperand.A:
result = Registers.A;
break;
default:
throw new ArgumentException(nameof(_addressState.SourceA));
}
}
// Read Source
ReadSource(_addressState.SourceA, ref _addressState.ResultA);
ReadSource(_addressState.SourceB, ref _addressState.ResultB);
// Do Operation
switch (_addressState.Operation)
{
case AddressOperation.None:
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
case AddressOperation.Inc:
_addressState.ResultA++;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
case AddressOperation.Dec:
_addressState.ResultA--;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
case AddressOperation.BitTest:
if (_addressState.AffectFlags)
{
Status.Z = (_addressState.ResultA & _addressState.ResultB) == 0;
Status.N = (_addressState.ResultB & 0x80) != 0;
Status.V = (_addressState.ResultB & 0x40) != 0;
}
break;
case AddressOperation.Compare:
if (_addressState.AffectFlags)
{
Status.C = _addressState.ResultA >= _addressState.ResultB;
UpdateNZ((byte)(_addressState.ResultA - _addressState.ResultB));
}
break;
case AddressOperation.And:
_addressState.ResultA &= _addressState.ResultB;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
case AddressOperation.Or:
_addressState.ResultA |= _addressState.ResultB;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
case AddressOperation.Adc:
{
var value = (short)(_addressState.ResultA + _addressState.ResultB + (Status.C ? 1 : 0));
if (_addressState.AffectFlags)
{
UpdateCV(_addressState.ResultA, _addressState.ResultB, value);
}
_addressState.ResultA = (byte)value;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
}
break;
case AddressOperation.Rol:
{
var c = Status.C;
if (_addressState.AffectFlags)
{
Status.C = (_addressState.ResultA & 0x80) != 0;
}
_addressState.ResultA = (byte)((_addressState.ResultA << 1) | (Status.C ? 1 : 0));
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
}
break;
case AddressOperation.Asl:
{
if (_addressState.AffectFlags)
{
Status.C = (_addressState.ResultA & 0x80) != 0;
}
_addressState.ResultA = (byte)(_addressState.ResultA << 1);
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
}
break;
case AddressOperation.Xor:
_addressState.ResultA ^= _addressState.ResultB;
if (_addressState.AffectFlags)
{
UpdateNZ(_addressState.ResultA);
}
break;
default:
throw new ArgumentException(nameof(_addressState.Operation));
}
// Write Destination
switch (_addressState.Destination)
{
case AddressOperand.None:
break;
case AddressOperand.Memory:
_masterClient.Value = _addressState.ResultA;
_masterClient.Write(_addressState.MemoryAddress);
break;
case AddressOperand.X:
Registers.X = _addressState.ResultA;
break;
case AddressOperand.Y:
Registers.Y = _addressState.ResultA;
break;
case AddressOperand.A:
Registers.A = _addressState.ResultA;
break;
case AddressOperand.S:
Registers.S = _addressState.ResultA;
break;
case AddressOperand.PC:
Registers.PC = _addressState.MemoryAddress;
break;
default:
throw new ArgumentException(nameof(_addressState.Destination));
}
}