two types of error control protocols exist in canopen: heartbeat and node/lifeguarding. for new designs, cia recommends the heartbeat protocol.
1) heartbeat:
the canopen device transmits its heartbeat cyclically. the cycle time is called producer heartbeat time and configured in object 1017h. the heartbeat consumer (e.g. the canopen manager) evaluates on reception of the heartbeat message, whether e.g. the related device is still working properly or not and remains in the correct network state. the heartbeat consumer capability is configured in object 1016h (e.g. within the canopen manager). in this object the period of time is configured, in which at least one heartbeat message has to be received from the related heartbeat producer.
2) node/life guarding:
guarding is an outdated method of checking whether the device to be guarded is still working in the correct network state or not. therefore e.g. the canopen manager requests the error control message via a can remote frame (rtr). the device to be guarded replies with a can data frame, which indicates the current nmt state. as this is an rtr-based service, the heartbeat protocol is recommended for error control purposes in new designs.
