Which products are affected?
EPM-T110 (CAN Gateway V1.2)
EPM-T111 (CAN Gateway ECO V1.2)
EPM-T830 (8x dig. I/O compact)
EPM-T831 (16x dig. I/O compact, single-wire conductor)
EPM-T832 (32x dig. I/O compact)
EPM-T833 (16x dig. I/O compact, three-wire conductor)
What happens?
After a NodeGuarding event (e.g. triggered by a communication interruption) the CAN gateway returns an invalid response to a new NodeGuarding telegram of the CAN Master.
If a Lenze PLC target system serves as CAN Master (Servo PLC, Drive PLC, ECS axis modules) the L_CanDSxNodeGuarding function block of the LenzeCanDSxDrv.lib library indicates error number -9 (= response received from the bus device to be monitored is invalid) at the nState output.
When does the problem occur?
The response to a NodeGuarding telegram includes a toggle bit. Contrary to the CANopen specification the CAN gateway resets the toggle bit to 0 after a NodeGuarding event or when the CAN state has changed from Operational to Pre-Operational. As a result, the response of the CAN gateway is rejected as invalid by the CAN Master.
According the CANopen specification it is only allowed to reset the toggle bit in the states PowerOn, ResetNode and ResetCommunication.
Possible diagnostics?
None.
Short-term measures/recommendations?
Use the heartbeat function to monitor the CAN devices.
Evaluation:
NodeGuarding is a monitoring mechanism in order to ensure the functionality of system bus devices. If this monitoring mechanism has been activated once it cannot be reactivated due to the function restriction described before.
