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PD42-x-1670 CANopen Firmware Manual Firmware Version V2.0 | Document Revision V1.0 2018-Nov-07
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2.2 NMT State Machine
The nite state machine (FSM) or simply state machine is a model of behavior composed of a nite number
of states, transitions between those states, and actions. It shows which way the logic runs when certain
conditions are met.
Starting and resetting the device is controlled via the state machine. The NMT state machine consists of
the states shown in gure 1.
Pre-operational
Operational
Stopped
Initialization
ID / Boot-up
Figure 1: NMT State Machine
After power-on or reset the device enters the Initialization state. After the device initialization is nished,
the device automatically transits to the
Pre-operational
state and indicates this state transition by send-
ing the boot-up message. This way the device indicates that it is ready to work. A device that stays in
Pre-operational state may start to transmit SYNC-, time stamp- or heartbeat message. In contrast to the
PDO communication that is disabled in this state, the device can communicate via SDO.
The PDO communication is only possible within the
Operational
state. During Operational state the
device can use all supported communication objects.
A device that was switched to the
Stopped
state only reacts on received NMT commands. In addition the
device indicates the current NMT state by supporting the error control protocol during Stopped state.
The transitions between states are made by issuing a network management (NMT) communication object
to the device. The NMT protocols are used to generate state machine change commands (e.g. to start and
stop the device), detect remote device boot-ups and error conditions.
The Heartbeat message of a CANopen device contains the device status of the NMT state machine and is
sent cyclically by the CANopen device.
The NMT state machine (or DS301 state machine) is not to be confused with the DS402 state machine.
There is only one NMT state machine for the entire device, but for each motor there is a DS402 state
machine which controls the motor. There are no links between these state machines, with one exception:
When the NMT state machine is being switched to the stopped state, all DS402 state machines that are in
OPERATION_ENABLED state will be switch to FAULT state.
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