BECKHOFF AX2000 CANopen communication profile - Manual (Page 15)

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:
S
O
M
COB-ID
R
T
R
CTRL Data Segment CRC
A
C
K
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
CANopen for AX2000/2500 15
BECKHOFF
07/2007
CANopen communication profile