Node Guarding and Heartbeat

Testing the functionality of a CAN node is particularly required if the node does not continuously send messages (cyclic PDOs). Two mechanisms can alternatively be used to monitor the CANopen® nodes. When the node guarding protocol is used, the NMT master sends messages to the available CANopen® slaves which have to respond to these messages within a certain time period. Therefore, the NMT master is able to detect if a node fails. Furthermore, the heartbeat protocol can be used with CANopen®. In this case, each node automatically sends a periodic message. This message can be monitored by each other subscriber in the network.