3
CANopen access procedure
Festo – GDCP-CMMP-M3/-M0-C-CO-EN – 1510b – English
39
3.6
Network Management (NMT Service)
All CANopen equipment can be triggered via the Network Management. Reserved for this is the identifi
er with the top priority (000
h
). By means of NMT, commands can be sent to one or all controllers. Each
command consists of two bytes, whereby the first byte contains the command specifier (CS) and the
second byte the node ID (NI) of the addressed controller. Through the node ID zero, all nodes in the
network can be addressed simultaneously. It is thus possible, for example, that a reset is triggered in all
devices simultaneously. The controllers do not acknowledge the NMT commands. Successful comple
tion can only be determined indirectly (e.g. through the switch-on message after a reset).
Structure of the NMT Message:
000
h
2
CS
NI
Identifier: 000
h
Command specifier
Data length
Node ID
For the NMT status of the CANopen node, statuses are established in a status diagram. Changes in
statuses can be triggered via the CS byte in the NMT message. These are largely oriented on the target
status.
Stopped (04
h
)
Power On
Reset Communication
Pre-Operational (7F
h
)
Operational (05
h
)
Reset Application
aE
aD
aC
aB
7
8
6
9
aJ
aA
5
2
3
4
Fig. 3.2
Status diagram
