DVP-ES2-EX2-SS2-SA2-SX2-Operation Manual

7 CANopen Function and Operation
The data format for RxPDO and TxPDO is as follows.
COB-ID Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
Object
identifier
‣ SDO (service data object)
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 visit mode of the SDO is
“client/server” mode. The mode which is visited is the SDO server. Every CANopen device
has at least one service data object which provides the visit channel for 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 visit. After the SDO client sends the reading/writing request, the
SDO server replies. The client and the server can stop the transmission of the SDO .The
requested message and the reply message are divided by 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 format of the requested message:
Data
COB-ID Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
600(hex) Requested Object index
+Node-ID code LSB MSB
Object
Requested data
subindex bit7-0 bit15-8 bit23-16 bit31-24
The definition of the requested code in the requested message:
Request code
(hex)
Description
23 Writing the 4-byte data
2B
2F
Writing the 2-byte data
Writing the 1-byte data
40 Reading the data
80 Stopping the current SDO function
The format of the reply message:
COB-ID Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
580(hex)
+Node-ID
Reply Object index
code LSB MSB
Object
Reply data
subindex bit7-0 bit15-8 bit23-16 bit31-24
The definition of the reply code in the reply message:
Reply code (hex)
Description
43 Reading the 4-byte data
4B
Reading the 2-byte data
4F
Reading the 1-byte data
60 Writing the 1/2/4-byte data
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