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EtherCAT Information
3.2 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)
0x0000-0x0FFF
0x1000-0x1FFF
0x2000-0x5FFF
0x6000-0x9FFF
0xA000-0xFFFF
Figure 2: Structure of the object dictionary
3.3 Process and Service Data Objects
Process Data Object (PDO)
Process Data Objects manage the process data exchange, e.g. the cyclical
transmission of the position value.
Service Data Object (SDO)
Service Data Objects manage the parameter data exchange, e.g. the acyclical
execution of the preset function.
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 3: Comparison of PDO/SDO characteristics
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Object
Data type definitions
CoE communication profile range (CiA DS-301)
Manufacturer-specific profile range
Device profile range (CiA DS-406)
Reserved
TR - ECE - BA - DGB - 0127 - 04
Printed in the Federal Republic of Germany
06/20/2017
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