CANopen Communication
FC5101 and FC5102
37
Version: 2.0
5
CANopen Communication
5.1
Network Management
Simple Boot-Up
CANopen allows the distributed network to boot in a very simple way. After initialization, the modules are
automatically in the
Pre-Operational
state. In this state it is already possible to access the object directory
using service data objects (SDOs) with default identifiers, so that the modules can be configured. Since
default settings exist for all the entries in the object directory, it is in most cases possible to omit any explicit
configuration.
Only one CAN message is then required to start the module: Start_Remote_Node: Identifier
0
, two data
bytes: 0x01, 0x00. It switches the node into the
Operational
state.
Network Status
The states and the state transitions involved as CANopen boots up can be seen from the state diagram:
Fig. 33: CANopen bootup state diagram
Pre-Operational
After initialization the Bus Coupler goes automatically (i.e. without the need for any external command) into
the
Pre-Operational
state. In this state it can be configured, since the service data objects (SDOs) are
already active. The process data objects, on the other hand, are still locked.
Operational
In the
Operational
state the process data objects are also active.
If external influences (such as a CAN error, or absence of output voltage) or internal influences (such as a K-
Bus error) mean that it is no longer possible for the Bus Coupler to set outputs, to read inputs or to
communicate, it attempts to send an appropriate emergency message, goes into the error state, and thus
returns to the
Pre-Operational
state. In this way the NMT status machine in the network master can also
immediately detect fatal errors.
Stopped
In the
Stopped
state (formerly:
Prepared
) data communication with the Coupler is no longer possible - only
NMT messages are received. The outputs go into the fault state.
