Lenze I/O system 1000 System Manual - Manual (Page 250)

CANopen communication
About CANopen
Structure of the CAN data telegram
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250 EDSIO1000 EN 7.0
8 CANopen communication
8.1 About CANopen
The I/O system supports the communication module 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 was developed as a universal protocol.
However, as the practice shows, applications with CAL were too complex for the users.
CANopen provides a uniform and simple structure for connecting the CAN devices of the
various manufacturers.
8.1.1 Structure of the CAN data telegram
Control field CRC delimit. ACK delimit.
Start RTR bit CRC sequence ACK slot End
Identifier User data (0 ... 8 bytes)
l Network management
l Process data
l Parameter data 1 bit 11 bits 1 bit 6 bits 15 bits 1 bit 1 bit 1 bit 7 bits
Fig. 8−1 Basic structure of the CAN telegram
)
Note!
Only the identifier and the user data are relevant to the user. All other data of
the CAN telegram are automatically processed by the system.
8.1.2 Identifier
The principle of CAN communication is based on a message−oriented data exchange
between a transmitter and many receivers. Therefore, all nodes can transmit and receive
more or less at the same time.
The so−called identifier in the CAN telegram, also called COB−ID (Communication Object
Identifier)), controls which node is to receive a transmitted message. In addition to the
addressing, the identifier contains information on the priority of the message and the type
of user data.
The identifier consists of a ’basic identifier’ and the node address of the device to be
approached:
Identifier = Basic identifier + node address
ƒ This node address is set with the coding switch at the module(
¶ 32).
ƒ Network management and sync telegram only require the basic identifier.
ƒ The identifiers can also be set individually( ¶ 256).