The IO-Link protocol allows a port to be operated in one of four different operating modes.

1.Operating Mode IO-Link 
The first mode is the IO-Link mode. This means that the port is used for communication.
2. DI Operating Mode

The second is the DI mode. In this case, the port acts like a digital input device.

3. DQ Operating Mode

The third mode is the DQ mode. In this case, the port acts like a digital output device.

4. Deactivated Operating Mode

the last mode is out of service or Deactivated. it means that the port is not assigned to any other modes.