ElmoMC CANopen DS 301 Implementation Guide - Manual (Page 21)

Chapter 4: Service Data Objects (SDOs)
SimplIQ digital servo drives use a single transmit server SDO (COB 581h-6ffh) and a single
receive server SDO (COB601h-67fh). This is according to CiA definitions and priority
allocations for 11-bit addressing.
When using SDOs, it is important to remember that:
ƒ
An SDO has a lower priority than a PDO.
ƒ An SDO session is not complete until it is confirmed.
For example, if an SDO is used to change a PDO mapping, the SDO should be issued only
after the last session in which the PDO is completed, and the newly-mapped PDO should
not be used until the SDO mapping change is confirmed.
SDOs implement the CMS multiplexed domain protocols.
Notes:
ƒ
In an SDO data exchange, each client message may be backed by one and only
one server message.
ƒ An SDO carries a toggle bit, which varies in every consecutive message of a
domain transfer, so that the loss of a single message can be tracked.
ƒ An SDO transfer can be terminated using the special “Abort domain transfer”
message.
ƒ An SDO message carries a maximum of seven bytes of data. One byte (the header
byte) is always dedicated to overhead data.
ƒ The length of an SDO message is always eight bytes, even if some of them are
unused. Unused data bytes are marked as such in the message header.
ƒ The maximum length of payload data in an expedited SDO is four bytes.
CANopen DS 301 Implementation Guide Service Data Objects (SDOs)
MAN-CAN301IG (Ver. 2.1)
4-1