Technical Manual
WDGA with CANopen-Interface
5 - General information about CAN
© Wachendorff Automation GmbH & Co. KG
14
Rev.1.24
The communication profile defines the basic services and parameters of a CANopen
device (e.g. service data objects SDOs, process data objects PDOs, used CAN-IDs,
etc.).
The device profile defines the specific functions of a device family (e.g. encoders, i/o
devices, ...). For encoders the device profile is the encoder profile CiA 406.
5.3 Specifications and profiles
5.3.1 Overview
The CANopen specifications were defined by the CiA in Draft Standards. Concerning
the WDGA encoders the following specifications are from special importance:
Specification
Description
CiA 301
Application Layer and Communication Profile
CiA 303
Cabling/pin assignment, Representation of units, Indicator specification
CiA 305
Configuration of baudrate und node ID via LSS
CiA 306
Electronic Data Sheet
CiA 406
Device-/Application-profile
Table 5.2: Draft Standards
5.3.2 Mechanisms of communication
There are several different CANopen communication services:
SDO
Service Data Object
Use:
for access to the object dictionary. There is one single SDO-channel.
Two identifiers are assigned to the SDO channel, one for each direction of
transmission.
For SDO the 8 byte CAN frame is divided into 1 byte command, a multiplexor of 2 byte
index and 1 byte sub index of the object dictionary, and 4 byte of payload. For bigger
payloads either segmented or block transfer is used.
A SDO transmission will always be acknowledged by the receiver. In case of a failure
an "abort message" is send. The internal delay time of the WDGA encoders is 1
millisecond maximum.
PDO
Process Data Object
Use:
for transmission of process data. The WDGA encoders provide up to four PDOs.
A PDO uses the full length of the data area of a CAN frame (8 bytes) for the process
data without additional overhead.
Summary of Contents for WDGA CANopen
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