Baumer BA_DSRT_22DJ - Handbuch (Seite 17)

Manual_CANopen_StrainLink_EN_V3_05.doc 17/65 Baumer
22.07.11/dam Frauenfeld, Switzerland
PDO message structure:
4.4.2 Service Data Objects (SDOs)
Specific communication objects, Service Data Objects (SDOs), are used for direct access to CANopen
devices. Entries in the object directory can be read and written using these SDOs. Communication always
takes place as a logical 1:1 connection (peer-to-peer) between two nodes (usually, the master is the
configuring node and a normal bus user is the node to be configured).
As a result of the direct connection, a response is expected for every request. This can be compared to a
connection via radio. Every request must receive a response even if the device is incapable of executing or
responding to the request or even if the request itself contains errors. Such a negative response is known as
an abort message. In addition to the 4-byte error code (cause of the abort), the abort message contains the
object address which was to be accessed.
SDO message structure
CS MUX
MUX Not used
CS MUX
MUX DATA
DATA
CS
Not used
CS
Server Client SDO Download
SDO Download-Answer
SDO Upload
SDO Upload-Answer
Server-to-Client-CAN-ID for Standard-SDO = 600h + NodeID
Client-to-Server-CAN-ID for Standard-SDO = 580h + NodeID
DLC = 8
CS = command specifier
MUX = 16-bit Index and 8-Bit Subindex