Service Data Objects (Sdo); Sdo Download - ABB FCAN-01 User Manual

124 Communication protocol

Service Data Objects (SDO)

Service Data Objects are mainly used for transferring non-time
critical data, for example, parameter values. SDOs provide access
to the entries in the device Object Dictionary.
If 4 bytes (or less) of data is to be transmitted, an Expedited
transfer SDO message can be used. Larger quantities of data can
be segmented, that is, split between several CAN messages.
The following services can be applied to SDO depending on the
service requirements:
•
SDO Upload, which can be divided into
•
Initiate SDO Upload
•
Upload SDO Segment.
•
SDO Download, which can be divided into
•
Initiate SDO Download
•
Download SDO Segment.
•
Abort SDO Transfer
With expedited transfer all data is transferred during the
initialization phase (Initiate SDO Upload/Download). With
segmented transfer only part of the data is transferred during the
initialization phase and the rest of the data is transferred during the
Upload/Download SDO Segment phase.
The COB IDs for the SDO communication are:
•
Client to Server (Master to Slave): 600h + Node ID
•
Server to Client (Slave to Master): 580h + Node ID.


SDO Download

Through this service the client of an SDO downloads data to the
server (owner of the Object Dictionary).
The data, the multiplexor (index and subindex) of the data set that
is downloaded and the data size are indicated to the server. The
service is confirmed. The remote result parameter will indicate the
success or failure of the request. In case of a failure, an Abort SDO
Transfer request has to be executed.