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4.2.2.5.2 NMT services for connection monitoring
Connection monitoring enables an NMT master to detect the failure of an NMT slave
and/or an NMT slave to detect the failure of the NMT master:
•
Node Guarding
:
An NMT master monitors an NMT slave
with this service
•
Life Guarding
:
An NMT slave monitors an NMT master
with this service
In the case of
Node Guarding
, the NMT master requests the status of an NMT slave
at regular intervals. If no return message is received within a defined time interval, the
NMT master assumes a failure of the NMT slave.
If
Life Guarding
is active, the NMT slave expects such a status request from the NMT
master within a defined time interval.
The NMT services for connection monitoring use the function code
1110 bin
, so
COB-ID 0x700+Node ID
.
Object no. Description
0x100C
Guard Time [ms]
0x100D
Life Time Factor
After expiry of the time interval
Life Time = Guard Time x Life Time Factor [ms]
at the latest, the NMT slave expects a status query from the
master.
If the Guard Time = 0, the corresponding NMT slave is not
monitored by the master.
If the Life Time = 0, Life Guarding is switched off.
Table 11: Parameters for NMT services