Baumer BA_DSRT_22DJ - Handbuch (Seite 21)

Manual_CANopen_StrainLink_EN_V3_05.doc 21/65 Baumer
22.07.11/dam Frauenfeld, Switzerland
4.4.5 Node guarding and Heartbeat
CANopen provides the following capabilities to determine the ability of the network nodes to function:
•
Automatic transmission of a heartbeat message by the network nodes (Heartbeat principle)
•
Cyclic querying of the node state by the NMT master (Node guarding principle)
With node monitoring according to the Heartbeat principle, every node automatically transmits a message at
regular intervals. This message can be monitored by every node in the network. The interval between two
heartbeat messages can be set in object 1017h.
With the Node guarding protocol, the NMT master sends messages to the CANopen slaves that then
respond within a defined time. The lack of a response can only be detected by the NMT master. If the NMT
master fails, the entire network is paralyzed. For this reason, and because of the higher bus load (caused by
two CAN messages per monitoring interval), Node guarding has almost completely been replaced by
Heartbeat monitoring.
The monitoring message of the nodes contains the COB ID 700h + the node ID of the sender. The only data
byte transmitted contains the device state (Pre-Operational, Operational, Stopped) of the sender.
Node state
Node state
DLC = 1
CAN-ID = 700h + NodeID
Inquiry
Inquiry
Node state values
4 = Stopped
5 = Operational
127 = Pre-Operational
Indication(s)
Indication(s)
Heartbeat
producer
time (1017h)
in ms
Heartbeat
consumer
time (1016h)
in ms
Indication
Heartbeat
event
Heartbeat producer Heartbeat consumer