Recognizing invalid data

Each EtherCAT slave has the so-called WCState bit, which signals error-free EtherCAT communication if the value = 0. However, if the WCState is set to 1, an error has occurred during EtherCAT transmission and the process data is invalid.

If, for example, the 230 V at the input is switched off, the output voltage slowly drops. As soon as the output voltage falls below the voltage required for EtherCAT communication, no more data is transmitted.
The output voltage therefore remains at the last transmitted value, although in reality it continues to fall.
However, as EtherCAT communication has been interrupted, WCState = 1 signals that the process data and in particular the data for the output voltage are no longer valid.

Invalid process data when switching off the input voltage.
Left: Normal operation, WCState bit = 0.
Right: Input voltage has been switched off, the output voltage remains at the last transmitted value, WCState = 1 indicates the invalidity of the process data.