
4th edition, 9-11-2018
7000.05050, 4th edition, 9-11-2018
7000.05050
CANopen protocol description
21
3.5
SDO (Service Data Object)
The SDO reads and describes parameters in the OV (object dictionary). The SDO accesses the
object dictionary via the 16-bit index and the 8-bit subindex. At the request of the client
(PC, PLC (programmable logic controller)) the Motion Controller makes data available
(upload) or receives data from the client (download).
Tab. 7:
General structuring of the SDO user data
Tab. 8:
Distribution of the SDO types of transmission
Only the expedited transfer is described in this document. The segmented transfer is
described in CiA 301.
3.5.1
Expedited transfer
SDO messages are always size 8 bytes.
Read OD entries (Client-to-Server, Upload-Request)
Server-to-Client, Upload-Response
The command specifier CS(0x4x) specifies the number of valid data bytes in D0 to D3 and
the transfer code. The command specifier is coded as follows:
CS = 0x4F, 1 data byte in D0
CS = 0x4B, 2 data bytes in D0 to D1
CS = 0x47, 3 data bytes in D0 to D2
CS = 0x43, 4 data bytes in D0 to D3
Byte0
Byte 1 to 2
Byte 3
Byte 4 to 7
Command specifier
16-bit index
8-bit subindex
4-byte parameter data
Type of transmission Number of bytes
Purpose
Expedited transfer
maximum 4 bytes Read and write individual numeric parameters
Segmented transfer
more than 4
bytes
Read text parameters (such as device name, firmware version) and
transmit data blocks (such as the trace buffer)
11-bit identifier
8 bytes user data
0x600 (1536d) +
node ID
0x40
Index LB
Index HB
Subindex 0
0
0
0
11-bit identifier
8 bytes user data
0x580 (1408d) +
node ID
CS(0x4x)
Index LB
Index HB
Subindex LLB (D0)
LHB (D1)
HLB (D2)
HHB (D3)