Communication via CAN bus
AG06
Date: 07.02.2018 Art. No. 85674 Mod. status 055/18 Page 36 of 114
9.3 CANopen protocol
The CANopen protocol is based on the CANopen communication profile CiA DS-301 V4.0 as
well as the device profile Drives and Motion Control CiA DSP-402 V2.0.
The details required for a better understanding and possible deviations are included in this
documentation.
9.3.1 Telegram setup
The data telegram of a CAN message consists of the following fields:
SOF:
Start of Frame start bit of the telegram
Identifier:
The Identifier field contains the identifier as well as bits for the recognition of the length of
the identifiers (11 or 29 bits). The identifier determines the priority of the message. Via
identifier, CANopen determines additionally the device address, channel selection as well as
data direction.
Control field:
Contains bits concerning the number of user data and determines whether a data frame or RTR
frame (Remote Transfer Request frame) is concerned.
Data field:
Contains up to 8 bytes of user data. The user data has a different meaning depending on the
hannel selection.
CRC:
Contains bits for error detection.
ACK/EOF:
The ACK/EOF field contains telegram acknowledgement bits as well as bits for determining the
end of telegram.
Fig. 8: Telegram setup
For a detailed description of the telegram please refer to the comprehensive CAN literature.
For simplification, only identifier and data field will be dealt with in the subsequent telegram
descriptions.
Control field
F
S
O
Identifier
CRC
ACK / EOF
CRC
Data field (max. 8byte)
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