Delta DVP-ES2/EX2/SS2/SA2/SX2/SE Cob-Id, Byte Object Data Identifier ¾ SDO service data object

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				Data
identifier

¾SDO (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:

COB-ID	Byte 0	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6	Byte 7
600（hex）Requested		Object index		Object		Requested data
+Node-ID	code	LSB	MSB	subindex	bit7-0	bit15-8	bit23-16	bit31-24

The definition of the requested code in the requested message:

Request code	Description
(hex)
23	Writing the 4-byte data
2B	Writing the 2-byte data
2F	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）	Reply	Object index		Object		Reply data
+Node-ID	code	LSB	MSB	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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