Fault Monitoring - Siemens SINAMICS S120 Commissioning Manual

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1.19 Fault monitoring

1.19 Fault monitoring
Fault monitoring services
The fault monitoring services are used to find errors within the CAN network.
Local faults within the device that, for example, lead to a reset or state change are not
affected.
The fault monitoring services are based on CANopen device messages sent out periodically.
There are two options for fault monitoring.
Node guarding
The NMT master sends monitoring queries using the node guarding protocol. If one of the
NMT slaves addressed does not reply within a certain time – the "Node lifetime" – or the
state of the NMT slave has changed, the NMT master informs its master application of this.
If the "Life guarding" method (NMT slave monitors the NMT master) is supported by the NMT
slave, it uses the entries for "Guard time" and "Lifetime factor" from its object directory to
determine its "Node lifetime". If the NMT slave is not addressed/monitored by the NMT
master within its "Node lifetime", it informs its local application of this using a "Life guarding
event". If the entries for "Guard time" and "Lifetime factor" in the slave's object directory are
at "0" (default setting), then the NMT slave does not monitor the NMT master.
Monitoring of the NMT slave starts when the first "Remote transmit request" (RTR) is
received from the NMT master via its COB ID. This usually happens during the bootup
phase.
Heartbeat
A "Heartbeat producer" (CANopen device) sends out heartbeat messages periodically. One
or several CANopen devices in the network recognize this heartbeat message. If the
"Heartbeat producer" misses a heartbeat cycle, the local application is informed using a
"Heartbeat event".
Note
For effective fault monitoring, one of the two methods must be activated.
"Node guarding" and "heartbeat" are deactivated in the basic setup.
Fault monitoring protocols
Node guarding protocol
The NMT master queries each NMT slave at regular time intervals (Node guard time). This
time interval can be different for each NMT slave. The slave's answer contains information
about its state. The "Node lifetime" results from the "Node guard time" multiplied by the
"Lifetime factor" and can be different for each NMT slave. If the NMT slave is not queried by
the NMT master during its "Node lifetime", a "remote node error" is displayed in the NMT
slave using a "Life guarding event".
A "Life guarding event" is created if
● the RTR ("Remote transmission request") is not confirmed within the "Node lifetime"
● the state reported by the NMT slave does not match the state expected by the NMT
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master.
Commissioning Manual, (IH2), V2.6, 10/2008 Edition, 6SL3097-2AA00-0BP3
CANopen interface