C.4 Sdo (Service Data Object) - Delta Electronics DVP15MC11T Operation Manual

C.4 SDO (Service Data Object)

SDO

The SDO is used to build the client/server relation between two CANopen devices. The client
device can read the data from the object dictionary of the server device, and write the data into
the object dictionary of the server device. The access mode of the SDO is "client/server" mode.
The mode which is accessed is the SDO server. Every CANopen device has at least one
service data object which provides the access channel to the object dictionary of the device.
SDO can read all objects in the object dictionary, and write all objects into the object dictionary.

The SDO message contains the index information and the subindex information which can be
used to position the objects in the object dictionary, and the composite data structure can easily
pass the SDO access. The trigger method of SDO belongs to the type of command response. In
other words, the SDO server must reply after the SDO client sends a read/write request. The
client and the server can stop the transmission of the SDO. The request message and response
message can be differentiated according to their different COB-IDs.

The SDO can transmit the data in any length. If the data length is more than 4 bytes, the data
has to be transmitted by segment. The last segment of the data contains an end flag.
The structures of the SDO requested message and reply message are as follows.
The formats of the request message and response message:

The format of the request message
COB-ID
600（hex）
+Node-ID

The definition of the request code in the request message:
Request code (hex)
23
2B
2F
40
80

The format of the response message
COB-ID
580（hex）
+Node-ID

The definition of the response code in the response message:
Response code
(hex)
43
4B
4F
60
80
Byte 0 Byte 1 Byte 2
Object index
Request
code
LSB MSB
Byte 0 Byte 1 Byte 2
Object index
Response
code
LSB MSB
Appendix C CANopen Protocol
Byte 3 Byte 4 Byte 5
Object index
bit7-0 bit15-8 bit23-16 bit31-24
Description
Writing the 4-byte data
Writing the 2-byte data
Writing the 1-byte data
Reading the data
Stopping current SDO function
Byte 3 Byte 4
Object
subindex
bit7-0 bit15-8 bit23-16 bit31-24
Description
Reading the 4-byte data
Reading the 2-byte data
Reading the 1-byte data
Writing the 1/2/4-byte data
Stopping the SDO function
Byte 6 Byte 7
Requested data
Byte 5 Byte 6 Byte 7
Response data
C-9
C_