Baumer G0-GB-GXP5W/S/H-GXU5W/S - Manual (Page 14)

Manual_G0-GB-GXP5-GXU5_406_EN.docx 14/48 Baumer IVO GmbH & Co. KG
20.11.12 Villingen-Schwenningen, Germany
Node and Life Guarding
The „CAN in Automation“ association CiA
recommend to use the new heartbeat protocol
(see next chapter).
To use the node guarding instead of heartbeat
protocol bit 5 of object 2110h has to be set.
To detect absent devices (e.g. because of
bus-off) that do not transmit PDOs regularly,
the NMT Master can manage a database,
where besides other information the expected
states of all connected devices are recorded,
which is known as Node Guarding. With cyclic
node guarding the NMT master regularly polls
its NMT slaves. To detect the absence of the
NMT master, the slaves test internally,
whether the Node Guarding is taking place in
the defined time interval (Life Guarding). The
Node Guarding is initiated by the NMT Master
in Pre-Operational state of the slave by
transmitting a Remote Frame.
The NMT Master regularly retrieves the actual
states of all devices on the network by a
Remote Frame and compares them to the
states recorded in the network database.
Mismatches are indicated first locally on the
NMT Master through the Network Event
Service. Consequently the application must
take appropriate actions to ensure that all
devices on the bus will got to a save state
"Communication error Object 1029h-1h".
Example for a nodeguarding protocol:
COB-ID Data/ Remote Byte 0
701h r 00h (0d)
701h d FFh (255d)
701h r 00h (0d)
701h d 7Fh (127d)
Possible NMT node states:
0: BootUp-Event
4: Stopped
5: Operational
127: Pre-operational
in other words, the encoder is in the pre-operational mode (7Fh = 127).