/// <summary>
/// Puts the device in save mode. From now on, every MIC pulse is recorded
/// </summary>
private void EnterSaveMode()
{
_currentMode = TapeOperationMode.Save;
_savePhase = SavePhase.None;
_micBitState = true;
_lastMicBitActivityTact = _cpu.Tacts;
_pilotPulseCount = 0;
_prevDataPulse = MicPulseType.None;
_dataBlockCount = 0;
SaveToTapeProvider?.CreateTapeFile();
}
/// <summary>
/// Processes the the change of the MIC bit
/// </summary>
/// <param name="micBit">MIC bit to process</param>
public void ProcessMicBit(bool micBit)
{
if (_currentMode != TapeOperationMode.Save ||
_micBitState == micBit)
{
return;
}
var length = _cpu.Tacts - _lastMicBitActivityTact;
// --- Classify the pulse by its width
var pulse = MicPulseType.None;
if (length >= TapeDataBlockPlayer.BIT_0_PL - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.BIT_0_PL + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.Bit0;
}
else if (length >= TapeDataBlockPlayer.BIT_1_PL - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.BIT_1_PL + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.Bit1;
}
if (length >= TapeDataBlockPlayer.PILOT_PL - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.PILOT_PL + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.Pilot;
}
else if (length >= TapeDataBlockPlayer.SYNC_1_PL - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.SYNC_1_PL + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.Sync1;
}
else if (length >= TapeDataBlockPlayer.SYNC_2_PL - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.SYNC_2_PL + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.Sync2;
}
else if (length >= TapeDataBlockPlayer.TERM_SYNC - SAVE_PULSE_TOLERANCE &&
length <= TapeDataBlockPlayer.TERM_SYNC + SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.TermSync;
}
else if (length < TapeDataBlockPlayer.SYNC_1_PL - SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.TooShort;
}
else if (length > TapeDataBlockPlayer.PILOT_PL + 2 * SAVE_PULSE_TOLERANCE)
{
pulse = MicPulseType.TooLong;
}
_micBitState = micBit;
_lastMicBitActivityTact = _cpu.Tacts;
// --- Lets process the pulse according to the current SAVE phase and pulse width
var nextPhase = SavePhase.Error;
switch (_savePhase)
{
case SavePhase.None:
if (pulse == MicPulseType.TooShort || pulse == MicPulseType.TooLong)
{
nextPhase = SavePhase.None;
}
else if (pulse == MicPulseType.Pilot)
{
_pilotPulseCount = 1;
nextPhase = SavePhase.Pilot;
}
break;
case SavePhase.Pilot:
if (pulse == MicPulseType.Pilot)
{
_pilotPulseCount++;
nextPhase = SavePhase.Pilot;
}
else if (pulse == MicPulseType.Sync1 && _pilotPulseCount >= MIN_PILOT_PULSE_COUNT)
{
nextPhase = SavePhase.Sync1;
}
break;
case SavePhase.Sync1:
if (pulse == MicPulseType.Sync2)
{
nextPhase = SavePhase.Sync2;
}
break;
case SavePhase.Sync2:
if (pulse == MicPulseType.Bit0 || pulse == MicPulseType.Bit1)
{
// --- Next pulse starts data, prepare for receiving it
_prevDataPulse = pulse;
nextPhase = SavePhase.Data;
_bitOffset = 0;
_dataByte = 0;
_dataLength = 0;
_dataBuffer = new byte[DATA_BUFFER_LENGTH];
}
break;
case SavePhase.Data:
if (pulse == MicPulseType.Bit0 || pulse == MicPulseType.Bit1)
{
if (_prevDataPulse == MicPulseType.None)
{
// --- We are waiting for the second half of the bit pulse
_prevDataPulse = pulse;
nextPhase = SavePhase.Data;
}
else if (_prevDataPulse == pulse)
{
// --- We received a full valid bit pulse
nextPhase = SavePhase.Data;
_prevDataPulse = MicPulseType.None;
// --- Add this bit to the received data
_bitOffset++;
_dataByte = (byte)(_dataByte * 2 + (pulse == MicPulseType.Bit0 ? 0 : 1));
if (_bitOffset == 8)
{
// --- We received a full byte
_dataBuffer[_dataLength++] = _dataByte;
_dataByte = 0;
_bitOffset = 0;
}
}
}
else if (pulse == MicPulseType.TermSync)
{
// --- We received the terminating pulse, the datablock has been completed
nextPhase = SavePhase.None;
_dataBlockCount++;
// --- Create and save the data block
var dataBlock = new TzxStandardSpeedDataBlock
{
Data = _dataBuffer,
DataLength = (ushort)_dataLength
};
// --- If this is the first data block, extract the name from the header
if (_dataBlockCount == 1 && _dataLength == 0x13)
{
// --- It's a header!
var sb = new StringBuilder(16);
for (var i = 2; i <= 11; i++)
{
sb.Append((char)_dataBuffer[i]);
}
var name = sb.ToString().TrimEnd();
SaveToTapeProvider?.SetName(name);
}
SaveToTapeProvider?.SaveTapeBlock(dataBlock);
}
break;
}
_savePhase = nextPhase;
}
/// <summary>
/// Leaves the save mode. Stops recording MIC pulses
/// </summary>
private void LeaveSaveMode()
{
_currentMode = TapeOperationMode.Passive;
SaveToTapeProvider?.FinalizeTapeFile();
}