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3.5 Object dictionary
The object dictionary structures the data of a POWERLINK 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
not used
0x0001-0x009F
Data type definitions
0x00A0-0x0FFF
reserved
0x1000-0x1FFF
Communication Profile Area (CiA DS-301, DS-302)
0x2000-0x5FFF
Manufacturer Specific Profile Area
0x6000-0x9FFF
Standardized Device Profile Area (CiA DS-406)
0xA000-0xBFFF
Standardized Interface Profile Area
0xC000-0xFFFF
reserved
Figure 4: Structure of the object dictionary
3.6 Process and Service Data Objects
Process Data Object (PDO)
Process Data Objects manage the process data exchange, e.g. the cyclical
transmission of the 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 5: Comparison of PDO/SDO characteristics
