Lenze DDS System bus CAN for PLC - Manual (Page 34)

System bus (CAN) for Lenze PLC devices
General information
2−22
l
PLC−Systembus EN 2.0
2.10.2 "Node Guarding"
In contrast to the "Heartbeat" monitoring mechanism, for the "Node Guarding" an enquiry message
from the monitoring node (NMT Master) is required.
Node
Life
Time
Node
Guarding
Event
Indication
Response
Confirmation
Confirmation
Response
Request
Request
Indication
Node
Guard
Time
NMT Master NMT Slave
RTR
t s
t s
RTR
Life
Guarding
Event
Node
Life
Time
1 8
1 8
t:
Stopped
Operational
Pre-Operational
Boot-Up Event
Toggle bit
s: NMT Slave state:
4
5
127
0
Fig. 2−8 "Node guarding" monitoring mechanism
·
The NMT master monitors each of the nodes to be monitored (NMT slave) cyclically using a
node−specific "Remote Transmission Request" telegram.
·
The NMT slave to be monitored returns its communication status as a response to this
request.
·
If the NMT master does not receive the message from the NMT Slave) to be monitored within
the set monitoring time (NodeLifeTime|, a "Node Guarding" event is displayed in its
application.
·
For the NMT slave to be monitored, however, a "Life Guarding" event is activated if its status
has not been enquired by the monitoring NMT master for longer than its "Node Life Time".