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CANopen Network Interface
1606218 02 08/2006 61
Access to Data by Explicit Exchanges (SDO)
What is an SDO? An SDO allows a device's data to be accessed by using explicit requests.
The SDO service is available when the device is in "Operational" or "Pre-
Operational" state.
Types of SDO There are two types of SDO:
Read SDOs (Download SDO)
Write SDOs (Upload SDO)
The Producer/
Consumer Model
The SDO protocol is based on a 'Producer/Consumer' model.
For a Download SDO
The client sends a request indicating the object to be read.
The server returns the data contained within the object.
For an Upload SDO
The client sends a request indicating the object to be written to and the desired
value.
After the object has been updated, the server returns a confirmation message.
For an unprocessed SDO
In both cases, if an SDO was not able to be processed, the server returns an error
code (abort code).