NMT State machine
The NMT state machine defines the communication status for CANopen devices.
Transition | Event |
---|---|
(1) | After power on the system goes directly to initialization state |
(2) | Once initialization is completed the system enters to Pre-operational state |
(3), (6) | Reception of Start remote node command |
(4), (7) | Reception of Enter pre-operational state command |
(5), (8) | Reception of Stop remote node command |
(9), (10), (11) | Reception of Reset node command |
(12), (13), (14) | Reception of Reset communication command |
NMT state initialization
The initialization state could be divided into three sub-states that are executed in a sequential way: Initializing (performs the basic CANopen initializations), Reset application (in where all manufacturer-specific and standardized profile area parameters are set) and Reset communication (where the communication profile and parameters are set).
At the end of initialization state the device sends a boot-up message and goes directly to Pre-Operational state.
NMT state pre-operational
In Pre-Operational state, the communication using SDO messages is possible. PDO message are not yet defined and therefore communication using these message is not allowed. The device will pass to Operational message after receiving a NMT start node command.
Normally the master puts a node in Pre-Operational state during the set-up and configuration of device parameters.
NMT state operational
In Operational state all kind of messages are active, even PDO messages.
NMT state stopped
When entering in Stopped state, the device is forced to stop all communications with the exception of the NMT commands. (Node Guarding & Life Guarding).
NMT states and communication object relation
Following table shows the relation between communication states and communication objects. Services on the listed communication objects may only be executed if the devices involved in the communication are in the appropriate communication states
| Pre-Operational | Operational | Stopped |
---|---|---|---|
NMT services | X | X | X |
NMT error control | X | X | X |
PDO |
| X |
|
SDO | X | X |
|
Sync object | X | X |
|
Emergency object | X | X |