Overview¶
Fundamental Properties and Fields of Application
CANopen® is a standardized layer 7 protocol used for decentralized industrial automation systems based on the Controller Area Network (CAN) and the CAN Application Layer (CAL). CANopen® is based on a communication profile containing the determination of basic communication mechanisms and their descriptions, such as the mechanisms used for exchanging process data in real-time or for sending alarm telegrams. This common communication profile is the basis for the various CANopen® device profiles. The device profiles describe the specific functionality and/or the parameters of a device class. Such device profiles are available for the most important device classes used in industrial automation, such as digital and analog I/O modules, sensors, drives, control units, regulators, programmable controllers or encoders. Further device profiles are projected.
The central element of the CANopen® standard is the device functionality description in an object directory (OD). The object directory is divided into one general area containing information about the device (e.g. device identification, manufacturer’s name, etc.) as well as communication parameters, and the device-specific area describing the particular functionality of the device. These properties of a CANopen® module are documented in the form of a standardized “electronic data sheet” (EDS file).
A CANopen® network can consist of a maximum of 128 modules, one NMT master and up to 127 NMT slaves. In contrast to the typical master-slave systems (e.g. PROFIBUS® systems), the meanings of the terms master and slave are different for CANopen®. In operational mode, all modules are independently able to send messages via the bus. Moreover, the master is able to change the operating mode of the slaves. The CANopen® master is normally implemented by a PLC or a PC. The bus addresses of the CANopen® slaves can be set in the range between 1 and 127. The device address results in a number of identifiers occupied by this module.
CANopen® supports transmission rates of 10 kbit/s, 20 kbit/s, 50 kbit/s, 125 kbit/s, 250 kbit/s, 500 kbit/s, 800 kbit/s and 1 Mbit/s. Each CANopen® device has at least to support a transmission rate of 20 kbit/s. Other transmission rates are optional.
Standardization
BOSCH CAN specification - version 2.0, part A and part B
ISO 11898
CiA DS 201 V1.1 - CAN Application Layer
CiA DS 301 V3.0 - CAL based Communication Profile for Industrial Systems
CiA DS 301 V4.02 - CANopen® Application Layer and Communication Profile
CiA DS 401 V2.1 - CANopen® Device Profile Generic I/O modules
CiA DS 402 V2.0 - CANopen® Device Profile Driver and Motion Control
CiA DS 406 V3.0 - CANopen® Device Profile Encoder
Terms, Definitions and Abbreviations
| CAL | CAN Application Layer |
| CAN | Controller Area Network |
| CiA | CAN in Automation international users and manufacturers group e.V. |
| DLC | Data Length Code |
| EDS | Electronic Data Sheet |
| ISO | International Standardization Organization |
| NMT | Network Management |
| OD | Object Directory |
| PDO | Process Data Object |
| RTR | Remote Transmission Request |
| SDO | Service Data Object |