3 CANopen access procedure
Festo – GDCP-CMMP-M3/-M0-C-CO-EN – 1510b – English 43
The producer_heartbeat_time can be stored in the parameter record. If the controller starts with a
producer_heartbeat_time not equal to zero, the bootup message is considered to be the first Heart
beat.
The controller can only be used as a so-called Heartbeat producer. The object 1016
h
(consumer_heartbeat_time) is therefore implemented only for compatibility reasons and always
returns 0.
3.9 Nodeguarding (Error Control Protocol)
3.9.1 Overview
The so-called Nodeguarding protocol can also be used to monitor communication between slave (drive)
and master. In contrast to the Heartbeat protocol, master and slave monitor each other: The master
queries the drive cyclically about its NMT status. In every response of the controller, a specific bit is
inverted (toggled). If these responses are not made or the controller always responds with the same
toggle bit, the master can react accordingly. Likewise, the drive monitors the regular arrival of the No
deguarding requests from the master: If messages are not received for a certain time period, the con
troller triggers error 12-4. Since both Heartbeat and Nodeguarding telegrams ( chapter 3.8) are sent
with the identifier 700
h
+ node number, both protocols cannot be active simultaneously. If both proto
cols are activated simultaneously, only the Heartbeat protocol is active.
3.9.2 Structure of the Nodeguarding Messages
The master's request must be sent as a so-called remote frame with the identifier 700
h
+ node number.
In the case of a remote frame, a special bit is also set in the telegram, the remote bit. Remote frames
have no data.
701
h
R 0
Identifier: 700
h
+ node number
Remote bit (Remote frames have no data)
The response of the controller is built up analogously to the Heartbeat message. It contains only 1 byte
of user data, the toggle bit and the NMT status of the controller ( chapter 3.6).
701
h
1 T/N
Identifier: 700
h
+ node number
Toggle bit / NMT status
Data length
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