PLC target system sends sync telegrams in millisecond cycles (elimination)

Which products are affected?
EPL-10200 (Drive PLC V7.1 and lower) 

What happens?
The PLC target system sends a sync telegram via the onboard system bus in a one millisecond cycle instead of using the transmitting cycle set under code C0369.

If the system bus network contains several stations with a set sync response (= automatic response of a CAN-Slaves to a sync telegram), the function restriction described before leads to a bus overload. As a result, communication problems occur, e. g. DDS logs off.

When does the problem occur?
The response described above may occur if the PLC target system is reset (e. g. via the DDS menu item: Online>Reset) or if a project has been downloaded to the PLC target system. Due to the communication problems mentioned above it may happen that DDS cannot be started by the PLC target system.

The function restriction does not occur if the PLC target system is automatically started after switch-on (C2104 = 1).

Possible diagnostics?
Check under code C0369 the sync transmitting cycle set and under code C2108 if the PLC target system is stopped. The transmitting cycle of the sync telegram can be observed by means of a CAN Analyzer such as PCAN View.

Short-term measures/recommendations?
Ensure saving with mains failure protection by setting code C2104 to 1 (automatic start after power switch-on). After mains switching of the PLC target system the PLC target system uses the sync transmitting cycle set under code C0369.

Evaluation:
After a project download or control reset communication problems may occur, which have been caused by a sync telegram which has been sent too often by the PLC target system. If the PLC target system is automatically started after mains switching this function restriction does not occur.