/// <summary>
/// Reads a byte of data from a specified port address
/// </summary>
public override byte ReadPort(ushort port)
{
bool deviceAddressed = true;
int result = 0xFF;
// check AY
if (AYDevice.ReadPort(port, ref result))
{
return((byte)result);
}
byte lowByte = (byte)(port & 0xff);
// Kempston joystick input takes priority over all keyboard input
// if this is detected just return the kempston byte
if (lowByte == 0x1f)
{
if (LocateUniqueJoystick(JoystickType.Kempston) != null)
{
InputRead = true;
return((byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine);
}
InputRead = true;
}
else if (UPDDiskDevice.ReadPort(port, ref result))
{
return((byte)result);
}
else
{
if (KeyboardDevice.ReadPort(port, ref result))
{
// not a lagframe
InputRead = true;
// process tape INs
TapeDevice.ReadPort(port, ref result);
}
else
{
deviceAddressed = false;
}
}
if (!deviceAddressed)
{
// If this is an unused port the floating memory bus should be returned
ULADevice.ReadFloatingBus((int)CurrentFrameCycle, ref result, port);
}
return((byte)result);
}
/// <summary>
/// Reads a byte of data from a specified port address
/// </summary>
/// <param name="port"></param>
/// <returns></returns>
public override byte ReadPort(ushort port)
{
bool deviceAddressed = true;
// process IO contention
ContendPortAddress(port);
int result = 0xFF;
// check AY
if (AYDevice.ReadPort(port, ref result))
{
return((byte)result);
}
// Kempston joystick input takes priority over all other input
// if this is detected just return the kempston byte
if ((port & 0xe0) == 0 || (port & 0x20) == 0)
{
if (LocateUniqueJoystick(JoystickType.Kempston) != null)
{
return((byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine);
}
InputRead = true;
}
else if (UPDDiskDevice.ReadPort(port, ref result))
{
return((byte)result);
}
else
{
if (KeyboardDevice.ReadPort(port, ref result))
{
// not a lagframe
InputRead = true;
// process tape INs
TapeDevice.ReadPort(port, ref result);
}
else
{
deviceAddressed = false;
}
}
if (!deviceAddressed)
{
// If this is an unused port the floating memory bus should be returned
// Floating bus is read on the previous cycle
long _tStates = CurrentFrameCycle - 1;
// if we are on the top or bottom border return 0xff
if ((_tStates < ULADevice.contentionStartPeriod) || (_tStates > ULADevice.contentionEndPeriod))
{
result = 0xff;
}
else
{
if (ULADevice.floatingBusTable[_tStates] < 0)
{
result = 0xff;
}
else
{
result = ReadBus((ushort)ULADevice.floatingBusTable[_tStates]);
}
}
}
return((byte)result);
}
/// <summary>
/// Reads a byte of data from a specified port address
/// </summary>
/// <param name="port"></param>
/// <returns></returns>
public override byte ReadPort(ushort port)
{
bool deviceAddressed = true;
// process IO contention
ContendPortAddress(port);
int result = 0xFF;
// check AY
if (AYDevice.ReadPort(port, ref result))
{
return((byte)result);
}
// Kempston joystick input takes priority over all other input
// if this is detected just return the kempston byte
if ((port & 0xe0) == 0 || (port & 0x20) == 0)
{
if (LocateUniqueJoystick(JoystickType.Kempston) != null)
{
return((byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine);
}
InputRead = true;
}
else
{
if (KeyboardDevice.ReadPort(port, ref result))
{
// not a lagframe
InputRead = true;
// process tape INs
TapeDevice.ReadPort(port, ref result);
}
else
{
deviceAddressed = false;
}
}
if (!deviceAddressed)
{
// If this is an unused port the floating memory bus should be returned
// Floating bus is read on the previous cycle
long _tStates = CurrentFrameCycle - 1;
// if we are on the top or bottom border return 0xff
if ((_tStates < ULADevice.contentionStartPeriod) || (_tStates > ULADevice.contentionEndPeriod))
{
result = 0xff;
}
else
{
if (ULADevice.floatingBusTable[_tStates] < 0)
{
result = 0xff;
}
else
{
result = ReadBus((ushort)ULADevice.floatingBusTable[_tStates]);
}
}
}
/*
* // Check whether the low bit is reset
* // Technically the ULA should respond to every even I/O address
* bool lowBitReset = (port & 0x0001) == 0;
*
* // Kempston joystick input takes priority over all other input
* // if this is detected just return the kempston byte
* if ((port & 0xe0) == 0 || (port & 0x20) == 0)
* {
* if (LocateUniqueJoystick(JoystickType.Kempston) != null)
* return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine;
*
* InputRead = true;
* }
* else if (lowBitReset)
* {
* // Even I/O address so get input from keyboard
* KeyboardDevice.ReadPort(port, ref result);
*
* TapeDevice.MonitorRead();
*
* // not a lagframe
* InputRead = true;
*
* // tape loading monitor cycle
* //TapeDevice.MonitorRead();
*
* // process tape INs
* TapeDevice.ReadPort(port, ref result);
* }
* else
* {
* // devices other than the ULA will respond here
* // (e.g. the AY sound chip in a 128k spectrum
*
* // AY register activate - on +3/2a both FFFD and BFFD active AY
* if ((port & 0xc002) == 0xc000)
* {
* result = (int)AYDevice.PortRead();
* }
* else if ((port & 0xc002) == 0x8000)
* {
* result = (int)AYDevice.PortRead();
* }
*
* // Kempston Mouse
*
* /*
* else if ((port & 0xF002) == 0x2000) //Is bit 12 set and bits 13,14,15 and 1 reset?
* {
* //result = udpDrive.DiskStatusRead();
*
* // disk drive is not yet implemented - return a max status byte for the menu to load
* result = 255;
* }
* else if ((port & 0xF002) == 0x3000)
* {
* //result = udpDrive.DiskReadByte();
* result = 0;
* }
*
* else if ((port & 0xF002) == 0x0)
* {
* if (PagingDisabled)
* result = 0x1;
* else
* result = 0xff;
* }
*//*
*
* // if unused port the floating memory bus should be returned (still todo)
* }
*/
return((byte)result);
}
/// <summary>
/// Reads a byte of data from a specified port address
/// </summary>
public override byte ReadPort(ushort port)
{
bool deviceAddressed = true;
int result = 0xFF;
// ports 0x3ffd & 0x7ffd
// traditionally thought to be write-only
if (port == 0x3ffd || port == 0x7ffd)
{
// https://faqwiki.zxnet.co.uk/wiki/ZX_Spectrum_128
// HAL bugs
// Reads from port 0x7ffd cause a crash, as the 128's HAL10H8 chip does not distinguish between reads and writes to this port,
// resulting in a floating data bus being used to set the paging registers.
// -asni (2018-06-08) - need this to pass the final portread tests from fusetest.tap
// get the floating bus value
ULADevice.ReadFloatingBus((int)CurrentFrameCycle, ref result, port);
// use this to set the paging registers
WritePort(port, (byte)result);
// return the floating bus value
return((byte)result);
}
// check AY
if (AYDevice.ReadPort(port, ref result))
{
return((byte)result);
}
byte lowByte = (byte)(port & 0xff);
// Kempston joystick input takes priority over keyboard input
// if this is detected just return the kempston byte
if (lowByte == 0x1f)
{
if (LocateUniqueJoystick(JoystickType.Kempston) != null)
{
return((byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine);
}
InputRead = true;
}
else
{
if (KeyboardDevice.ReadPort(port, ref result))
{
// not a lagframe
InputRead = true;
// process tape INs
TapeDevice.ReadPort(port, ref result);
}
else
{
deviceAddressed = false;
}
}
if (!deviceAddressed)
{
// If this is an unused port the floating memory bus should be returned
ULADevice.ReadFloatingBus((int)CurrentFrameCycle, ref result, port);
}
return((byte)result);
}