Inclination sensor JN
24
11 Emergency messages
Every inclination sensor supports EMCY messages which are transmitted in the
event of sensor, temperature, hardware or guarding errors.
If one of these errors occurs, the error register (OD index 1001h) and the pre-
defined error field (OD index 1003h) are updated.
After rectification of the error the device transmits an EMCY message with the
"error reset" code (0h) and the current state of the error and manufacturer status
register. The current device state ("pre-operational, operational or stopped") is not
influenced by the error states (except for guarding errors).
11.1 Failure monitoring
As in a CANopen network the nodes do not respond regularly in the case of
an event-controlled transmission, heartbeat and node guarding/life guarding
mechanisms are available for failure monitoring.
Only one of the two monitoring methods can be used.
11.1.1 Node guarding / life guarding
Node guarding is the monitoring of one or several nodes by the NMT master. The
NMT master periodically transmits an RTR telegram to the slave to be monitored
which responds with its own status and a toggle bit.
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).
11.1.2 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).