Baumer G1-G2-G0-GE-GB-GXxxx - Manual (Page 16)

Manual_CANopen_BIDE_EN.docx 16/52 Baumer IVO GmbH & Co. KG
21.11.12 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).