User Manual

CANopen Manual for TMCM-1140, TMCM-1160, and TMCM-1180 (Rev. 2.01 / 2017-JUL-26) 10
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2.2 NMT State Machine
The finite state machine (FSM) or simply state machine is a model of behavior composed of a finite
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 contains the
following states:
Pre-operational
Operational
Stopped
Initialization
ID / Boot-up
Figure 2.1 Overview CANopen NMT state machine
After power-on or reset the device enters the Initialization state.
After the device initialization is finished, the device automatically transits to the Pre-operational state
and indicates this state transition by sending 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 has to be 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
to 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.