Danaher Motion 07/06 Overview
M-S2-021-11 Initial Release 3
2. OVERVIEW
CANopen (Controller Area Network) is a development of the CIA (CAN-in-Automation) international user
and manufacturers group and is standardized in the European standard EN 50325-4. CANopen is a very
popular industrial communication system. CANopen was originally designed for motion-oriented machine
control networks, such as handling systems. It is used in many more industries, such as medical equipment,
off-road vehicles, maritime electronics, public transportation and building automation. CANopen products
are certified by the CIA user organization, guaranteeing worldwide compatibility.
CANopen provides standardized communication objects for realtime data (Process Data Objects, PDO),
configuration data (Service Data Objects, SDO), and special functions (Time Stamp, Sync message, and
Emergency message) as well as network management data (Boot-up message, NMT message, and Error
Control). All communication objects are listed in the Object Dictionary.
The Object Dictionary describes the complete functionality of a device by way of communication objects
and is the interface between the communication interface and the application program. CANopen supports
both cyclic and acyclic event driven communication. This makes it possible to reduce the bus load to a
minimum and maintain short reaction times. CANopen achieves high communication performance at low
baud rates, thus reducing EMC problems and minimizing cable cost.
Generic device profiles describe just the interface of a single device. Application profiles describe all the
device interfaces that are part of an application. Popular examples are the device profiles for I/O devices,
electric drives, encoders or transducer and closed loop controllers.
2. 1 COMMUNICATION PROFILE
CAUTION
It is assumed that the basic operating functions of the communication profile are known
and available as reference documentation.
The transmission method used is defined in ISO 11898 (Controller Area Network CAN for high-speed
communication). The Layer-1/2 protocol (Physical Layer/Data Link Layer) that is implemented in all CAN
modules provides, amongst other things, the requirements for data. Data transport or data request is made
by means of a data telegram (Data Frame) with up to 8 bytes of user data, or by a data request telegram
(Remote Frame). Communication objects (COBs) are labeled by an 11-bit Identifier (ID) that also
determines the priority of objects.
A Layer-7 protocol (Application Layer) was developed to decouple the application from the
communication. The service elements, provided by the Application Layer, make it possible to implement an
application across the network. These service elements are described in the CAN Application Layer (CAL)
for Industrial Applications. The communication profile CANopen and the drive profile are mounted on the
CAL. The basic structure of a communication object is shown in the following diagram:
SOM COB-ID RTR CTRL Data Segment CRC ACK EOM
SOM
Start of message
COB-ID
Communication Object Identifier (11-bit)
RTR
Remote Transmission Request
CTRL
Control Field (e.g. Data Length Code)
Data Segment
0 ... 8 byte (Data-COB)
0 byte (Remote-COB)
CRC
Cyclic Redundancy Check
ACK
Acknowledge slot
EOM
End of message
