4
EtherCAT interface
66
Festo – GDCP-CMMP-M3/-M0-C-CO-EN – 1510b – English
4.9
PDO Frame
Process Data Objects (PDO) are used for cyclic transmission of setpoint values and actual values
between master and slave. They must be configured in the “Pre-Operational” status by the master
before the slave is operated. They are then transmitted in PDO frames. These PDO frames have the
following structure:
All data of a PDO transfer are transmitted via PDO frames in CoE. These frames have the following
structure:
Process Data
Process Data
1...8 bytes
1...n bytes
Standard CANopen PDO Frame
Optional
Fig. 4.5
PDO Frame: telegram structure
Element
Description
Process Data
Data content of the PDO (Process Data Object)
Process Data
(optional)
Optional data content of additional PDOs
Tab. 4.13 PDO Frame: elements
To transmit a PDO via the EtherCAT-CoE protocol, in addition to the PDO configuration (PDO Mapping),
the Transmit and Receive PDOs must be assigned to a transmission channel of the Sync Manager
(
chapter 4.6.1 “Configuration of the Communication Interface”). The data exchange of PDOs for the
motor controller CMMP-AS-...-M3 takes place exclusively via the EtherCAT process data telegram pro
tocol.
The transfer of CANopen process data (PDOs) via acyclic communication (mailbox tele
gram protocol) is not supported by the motor controller CMMP-AS-...-M3.
As all data exchanged via the EtherCAT CoE protocol are forwarded directly to the internal CANopen
implementation in the motor controller CMMP-AS-...-M3, the PDO mapping is also implemented as
described in chapter 3.3 “PDO Message”. The figure below depicts this process:
