Image Processing Reference
In-Depth Information
the last stored parameters; on the contrary, default values are used. After initialization is
finished, a boot-up message is sent and the preoperational state is entered automatically.
•
Preoperational
: his state is used for configuring the device. As communication through
SDOs is available, entries of the OD can be remotely accessed (and changed) by a config-
uration application/tool. Communication through PDOs, instead, is not allowed yet.
•
Operational
: In this state all communications are permitted, and this usually corresponds
to a fully functional behavior for the device. Besides PDO communication, used to
exchange set-points and measured values, also SDOs are allowed. However, the access
to the OD might be somehow restricted.
•
Stopped
: In this state all communications are completely stopped (except for NMT ser-
vices). Furthermore, a specific behavior (that usually corresponds to a stopped device)
can be enforced, as described by the corresponding device profile.
The resulting behavior of the device can be described by means of the state diagram in Figure ..
Transitions are labeled through the following NMT services, whose meaning is self explanatory:
•
Start remote node
•
Stop remote node
•
Enter preoperational
•
Reset node
•
Reset communication
The NMT master can invoke these services for either one single slave at a time or all of them at the
same time (this is useful, e.g., for starting/halting simultaneously all devices in the network). Such
Entered
autonomously
Initialization
Power-on
or
H/W reset
Initializing
Reset node
Reset App.
Reset communication
Reset Comm.
Initialization finished—entered automatically
Enter preoperational
Preoperational
Stop remote node
Start remote node
Enter preoperational
Stopped
Start remote node
Stop remote node
Operational
FIGURE .
NMT state machine.
