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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.
Index (hex)
Object
0x0000-0x0FFF
Data type definitions
0x1000-0x1FFF
CoE communication profile range (CiA DS-301)
0x2000-0x5FFF
Manufacturer-specific profile range
0x6000-0x9FFF
Device profile range (CiA DS-402)
0xA000-0xFFFF
Reserved
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