Transmission Of Sdo Messages; Sdo Message Format - TR-Electronic CANopen+Multi-Sensor LP-46-K Benutzerhandbuch

CANopen information

3.5 Transmission of SDO messages

The transmission of SDO messages is done by the CMS "Multiplexed Domain"
protocol (CIA DS202-2).
With SDOs objects from the object dictionary can be read or written. It is an
acknowledged service. The so-called SDO client specifies in its request the
parameter, the access method (read/write) and if necessary the value. The so-called
SDO server performs the write or read access and answers the request with a
response. In the error case an error code gives information about the cause of error.
Transmit-SDO and Receive-SDO are distinguished by their function codes.
The measuring system (slave) corresponds to the SDO server and uses the following
function codes:
Function codes
11 (1011 bin)
12 (1100 bin)
Table 1: COB-IDs for Service Data Object (SDO)

3.5.1 SDO message format

The data field with max. 8 byte length of a CAN message is used by a SDO as follows:
CCS
Byte 0
Table 2: SDO message
The client command specifier (CCS) identifies whether the SDO is to be read or
written. In addition with a writing order, the number of bytes which can be written is
encoded in the CCS.
At the SDO response the CCS reports whether the request was successful. In the
case of a reading order the CCS gives additionally information about the number of
bytes, which could be read:
CCS
0x22
0x23
0x2B
0x2F
0x60
0x80
0x40
0x43
0x4B
0x4F
Table 3: SDO command codes
In the case of an error (SDO response CCS = 0x80) the data field contains a 4-byte
error code, which gives information about the error cause. Meaning of the error codes
see table Table 16 on page 180.
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Page 110 of 183
COB-ID
0x580 + Node ID
0x600 + Node ID
Index Sub-Index
Byte 1 Byte 2
Byte 3
Low High
Meaning
Writing request
Write 4 bytes
Write 2 bytes
Write 1 byte
Writing successfully
Error
Reading request
4 byte data read
2 byte data read
1 byte data read
TR - ELA - BA - DGB - 0016 - 04
Meaning
Slave  SDO Client
SDO Client  Slave
Data
Byte 4 Byte 5
Valid for
SDO Request
SDO Request
SDO Request
SDO Request
SDO Response
SDO Response
SDO Request
SDO response upon reading request
SDO response upon reading request
SDO response upon reading request
Printed in the Federal Republic of Germany
Byte 6 Byte 7
01/20/2017