Lenze EtherCAT control technology - Manual (Page 21)

DMS 3.1 EN 01/2011 TD17
L
21
Control technology | EtherCAT communication manual
The Lenze control system with EtherCAT
Brief description of EtherCAT
4.1.3.3 Working counter
Each EtherCAT datagram contains a working counter (WKC) which is incremented by each
slave after the data have been processed successfully.
In every cycle, the control unit compares the expected value of the working counter with
the value read back via the fieldbus. If the read-back value is lower than the expected value,
the telegram has not reached all addressed slaves. The control unit recognises this and
signals an error.
The working counter (WKC) can be used as a diagnostics option to check the processing of
the EtherCAT telegrams by the slaves.
Example
 10 slaves read/write process data in the Operational status
Expected value of the WKC: 10
 A cable break between the 8th and 9th slave causes the master to be unable to access
slave 9 and slave 10:
– Value of the restored WKC: 8
– An error response is initiated in the control.