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4
EtherCAT interface
Festo – GDCP-CMMP-M3/-M0-C-CO-EN – 1510b – English
65
4.8
SDO Frame
All data of an SDO transfer are transmitted via SDO frames in CoE. These frames have the following
structure:
6 bytes
2 bytes
1 byte
2 bytes
4 bytes 1...n bytes
1 byte
Mailbox Header
CoE Header
SDO Control Byte
Index
Sub-index
Data
Data
Mandatory Header
Standard CANopen SDO Frame
Optional
Fig. 4.4
SDO Frame: telegram structure
Element
Description
Mailbox Header
Data for mailbox communication (length, address and type)
CoE Header
Identifier of the CoE service
SDO Control Byte
Identifier for a read or write command
Index
Main index of the CANopen communication object
Sub-index
Sub-index of the CANopen communication object
Data
Data content of the CANopen communication object
Data (optional)
Additional optional data. This option is not supported by the motor controller
CMMP-AS-...-M3, as only standard CANopen objects can be addressed. The
maximum size of these objects is 32 bits.
Tab. 4.12 SDO Frame: elements
In order to transmit a standard CANopen object via one of these SDO frames, the actual CANopen SDO
frame is packaged in an EtherCAT SDO frame and transmitted.
Standard CANopen SDO frames can be used for:
–
Initialisation of the SDO download
–
Download of the SDO segment
–
Initialisation of the SDO upload
–
Upload of the SDO segment
–
Abort of the SDO transfer
–
SDO upload expedited request
–
SDO upload expedited response
–
SDO upload segmented request (max. 1 segment with 4 bytes of user data)
–
SDO upload segmented response (max. 1 segment with 4 bytes of user data)
All above-mentioned transfer types are supported by the motor controller
CMMP-AS-...-M3.
As the use of the CoE implementation of the CMMP-AS-...-M3 only allows the standard
CANopen objects to be addressed, whose size is restricted to 32 bits (4 bytes), only
transfer types with a maximum data length of up to 32 bits (4 bytes) are supported.