Lenze 931K - Manual (Page 16)

CANopen communication
About CANopen
Structure of the CAN data telegram
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16 KHB 13.0002−EN 4.1
5 CANopen communication
5.1 About CANopen
The CANopen protocol is a standardised layer 7 protocol for the CAN bus. This layer is based
on the CAN application layer (CAL), which has been developed as a universal protocol.
In practice, however, it became clear that applications with CAL were too complex for the
user. CANopen is a uniform, easy−to−use structure which has been developed to provide a
connection for CAN devices from different manufacturers.
5.1.1 Structure of the CAN data telegram
Control field CRC delimit. ACK delimit.
Start RTR bit CRC sequence ACK slot End
Identifier Data
length
User data (0 ... 8 bytes)
l Network management
l Process data
l Parameter data
1 bit 11 bits 1 bit 2 bits 4 bits 15 bits 1 bit 1 bit 1 bit 7 bits
Fig. 3 Basic structure of the CAN telegram
)
Note!
To the user, only the identifier, the data length and the user data are relevant.
All other data of the CAN telegram is automatically processed by the system.
5.1.2 Identifier
The principle of the CAN communication is based on a message−oriented data exchange
between one sender and many receivers. All nodes can send and receive
quasi−simultaneously.
The identifier in the CAN telegram − also called COB ID (communication object identifier) −
is used to control which node is to receive a sent message. In addition to the addressing,
the identifier contains information on the priority of the message and on the type of the
user data.
With the exception of the network management and the sync telegram, the identifier
contains the node address of the drive:
Identifier (COB ID) = basic identifier + adjustable node address (node ID)
The identifier assignment is specified in the CANopen protocol.
The ex works default setting of the basic identifier is: