CAN-8123/CAN-8223/CAN-8423 user’s manual (Revision 3.00, May/22/2009) ------
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5.1 SDO Communication Set
5.1.1 Upload SDO Protocol
Initiate SDO Upload Protocol
Before transferring the SDO segments, the client and server need to
communicate with each other by using the initiate SDO upload protocol. Via
the initiate SDO upload protocol, the SDO client will inform the SDO server
what object the SDO client wants to request. As well, the initiate SDO upload
protocol is permitted to transmit up to four bytes of data. Therefore, if the data
length of the object, which the SDO client can read, is equal to or less than the
permitted data amount, the SDO communication will be finished only by using
the initial SDO upload protocol, i.e. if the data upload is less enough to be
transmitted in the initiate SDO upload protocol, then the upload SDO segment
protocol will not be used. The communication process of this protocol is shown
as follows.