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3 CANopen communication profile

This chapter describes the basic services and Communication Objects of the CANopen communi

cation profile DS 301, which are used in the AX2000/2500.

It is assumed that the basic operating functions of the communication profile are known,

and available as reference documentation.

3.1 General description of CAN

The transmission method that is used here 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 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 commu-

nication. The service elements that are provided by the Application Layer make it possible to imple-

ment an application that is spread 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:

COB-ID

CTRL Data Segment CRC

EOM

SOM Start of message

COB-ID COB 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

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Beckhoff AX2000 CANopen communication profile Manual de usuario Pagina 15