STÖBER
9 | More about CANopen?
09/2019 | ID 442637.01
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9
More about CANopen?
The following sections summarize the key terms, services and relationships relating to CANopen.
9.1
CAN bus and CANopen
CAN and communication in CAN bus
The "Controller Area Network" (CAN) bus system is a real-time fieldbus for serial data transmission.
The individual tasks of a CAN bus are defined in what are called the layers. The actual CAN protocol corresponds to the
"Data Link Layer" (Layer 2) of the ISO/OSI reference model.
At this level, ordinary or manufacturer-specific CAN networks can be built and nodes (slaves) of different manufacturers can
be interconnected without any trouble. In the case of a shared line, the data flow itself is controlled by a protocol that
controls the access rights of the individual nodes—regardless of the manufacturer.
CAN provides many advantages: it serves a broad user base thanks to its real-time and multi-master capabilities, high fault
resistance and good availability. CAN is used primarily where high transmission rates and a simple, cost-effective
installation are required.
What is CANopen?
CANopen is the CAN-based communication protocol and the open standard for networking controllers, drives, encoders or
sensors, that is, all nodes in a CAN bus system. Both the functions of the intercommunicating nodes and the foundational
communication mechanisms are defined in CANopen. CANopen expands upon CAN with what is called the CAN application
layer (CAL = layer 7 of the ISO/OSI reference model). CANopen has been maintained by the organization CiA (CAN in
Automation e.v.) since 1996 and is codified as European standard EN 50325-4.
9.1.1
CANopen – Communication
CANopen stipulates that all bus nodes are to be bundled into separate classes with the same properties. Each of these
classes has its own "device profile," in which specific features, such as standard configurations, runtime behavior or error
handling, are defined along with all associated parameters.
All device profiles are organized in what is called an "object directory." All device profiles are based on their own
communication profile. This is where it is specified how the devices connected in a CAN-based network are addressed and
which mechanisms are used for exchanging process data or large amounts of data.
