Schneider Electric DS301 manual SDO message, example

IL•1F CANopen DS301 3 Basics

3.3.3SDO message

Put simply, an SDO message consists of the COB ID and the SDO data frame, in which up to 4 bytes of data can be sent. Longer data se- quences are distributed over multiple SDO messages with a special pro- tocol.

The device sends SDOs of up to 4 bytes data length (data). Greater amounts of data such as 8 byte values of the data type "Visible String 8" can be distributed over multiple SDOs and are transmitted successively in 7 byte blocks.

Example The following illustration shows an example of an SDO message.

SDO

581

COB-ID (581h)

0	1	2	3	4	5	6	7
43	00	10	00	92	01	02	00

Data

Subindex

Index

Command Code

Figure 3.11 SDO message, example

COB ID and data frame R_SDO and T_SDO have different COB IDs.

The data frame of an SDO messages consists of:

•Command code (ccd) in which the SDO message type and the data length of the transmitted value are encrypted

•Index and subindex which point to the object whose data is trans- ported with the SDO message

•Data of up to 4 bytes

Evaluation of numeric values Index and data are transmitted left-aligned in Intel format. If the SDO contains numerical values of more than 1 byte in length, the data must be rearranged byte-by-byte before and after a transmission.

581

	Index:			Data:
0	1	2	3	4	5	6	7
43	00	10	00	92	01	02	00

Hex: 10 00h 00 02 01 92h

Figure 3.12 Rearranging numeric values greater than 1 byte

0198441113586, V2.01, 11.2008

Fieldbus interface 27