ifm electronic JN2100 v.2.2.0 - Manual (Page 30)

Inclination sensor JN
30
If the status or toggle bit do not correspond to the response expected from the
guarding master or no response is given, the master assumes a slave error.
With this mechanism the node to be monitored can detect even the failure of
the guarding master.
To do so, two parameters are used. The interval time used by the guarding
master to check the sensor to be monitored is the guard time (100Ch).
The second parameter, the life time factor (100D h), defines a multiplier.
The product of guard time and life time factor defines the life time of the node
(node life time). This life time indicates the time after which the connection is
considered as interrupted.
Node life time = guard time × life time factor
If the sensor receives no guarding request from the master within this
configured time, it assumes a master failure. It transmits an emergency
telegram and returns to the "pre-operational" state. If one of the two parameters
is "0" (default setting), the master is not monitored (no lifeguarding).
12.1.2 Heartbeat
Heartbeat is a failure monitoring mechanism which needs no RTR telegrams. The
sensor cyclically transmits a heartbeat message which contains the device status
and can be monitored by the master. Heartbeat is activated as soon as a value
greater than "0" is entered in the register heartbeat interval time (OD index 1017h).
Heartbeat has a considerable influence on the bus load of the CANopen network - but generates a
bus load which is only half as high as node guarding / life guarding.