Moog ACV with CANopen bus interface
2 Access over CANopen
Network management state machine (NMT state machine)
B99224-DV018-D-211, Rev. A, October 2018
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The master controls the state transitions of each device in the network. After power-on, the device is initialized
and set to the state 'Pre-Operational' automatically. In this state reading and writing to its object dictionary via
the service data objects (SDO) is possible. The device can be configured by setting values and by preparing
the PDO transmission.
Afterwards the device can be switched into the 'Operational' state by the NMT command "Start Remote Node"
in order to start PDO communication. PDO communication can be stopped by the network master by simply
switching the remote node back to 'Pre-Operational' by using the command "Enter Pre-Operational".
With the "Stop Remote Node" command the master can force the slave(s) to the state 'Stopped'. In this state
no services besides network and error control mechanism are available. The NMT command "Reset Commu-
nication" resets the communication of the node. All communication parameters will be set to their defaults.
The application will be reset by the NMT command "Reset Node". This command resets all application param-
eter. All NMT commands use the COB-ID 0. The different NMT commands are distinguished by a command
specifier (CS) located in the first data byte of the message.
NMT state transitions are caused by
• Reception of an NMT node control service
• Hardware reset, or
• Node control services locally initiated by application events.
Services on the listed communication objects may only be executed if the CANopen device is in the appropri-
ate NMT state.
2.9.1 Network management (NMT) protocol (COB-ID: 0x000, 0x700)
The NMT master controls the NMT slave nodes using the following commands:
• Device control services for initialization and start-up of NMT slave nodes that want to take part in the dis-
tributed application.
• Node Guarding of NMT slave nodes.
The NMT commands are unconfirmed.
Transition
Description
(1)
At Power on the NMT state initialization is entered autonomously.
(2)
NMT state initialization finished - enter NMT state Pre-operational automatically (Boot-up message will be
sent).
(3)
Receive NMT command "start remote node" or by local control.
(4), (7)
Receive NMT command "enter pre-operational".
(5), (8)
Receive NMT command "stop remote node".
(6)
Receive NMT command "start remote node".
(9)
Receive NMT command "reset node".
(10)
Receive NMT command "reset communication".
Table 23: NMT state transitions
NMT states
Available services
SDO
PDO
EMCY
NMT
NMT Node
Guarding
'STOPPED'
x
x
'Pre-Operational'
x
x
x
x
'Operational'
x
x
x
x
x
Table 24: NMT states
