
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
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
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 |