Printed in the Federal Republic of Germany TR-Electronic GmbH 2016, All Rights Reserved
09/29/2020 TR-EMO-BA-GB-0022 v03 Page 25 of 153
4.5 Object dictionary
The object dictionary structures the data of an EtherCAT device in a clear tabular
arrangement. It contains all device parameters and all current process data, which are
therefore also accessible via the SDO.
CoE communication profile range (CiA DS-301)
Manufacturer-specific profile range
Device profile range (CiA DS-402)
Figure 7: Structure of the object dictionary
4.6 Process and Service Data Objects
Process Data Object (PDO)
Process Data Objects manage the process data exchange, e.g. the cyclical
transmission of the control- and status word, position value and target position etc.
Service Data Object (SDO)
Service Data Objects manage the parameter data exchange, e.g. the acyclical
parameter setting of non-time-critical parameters such as software limit switches,
direction of rotation etc.
The SDO provides an efficient communication mechanism for parameter data of any
size. A service data channel for parameter communication is formed between the
configuration master and the connected devices for this purpose. The device
parameters can be written to or read from the device object dictionary with a unique
frame handshake.
Important features of SDO and PDO
Figure 8: Comparison of PDO/SDO characteristics
To Next Page
Loading...
