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0198441113586, V2.01, 11.2008
IL•1F CANopen DS301 3 Basics
Fieldbus interface 29
Reading data The client starts a read request by sending the index and subindex that
point to the object or the object value whose value it wants to read.
The server confirms the request by sending the desired data. The SDO
response contains the same index and subindex. The length of the re-
sponse data is specified in the command code "ccd".
Figure 3.14 Reading a parameter value
Unused bytes in the data field are shown with a slash in the graphic. The
content of these data fields is not defined.
ccd coding The table below shows the command code for transmitting a read value.
It depends on the message type and the transmitted data length.
Table 3.6 Command code for transmitting a read value
Client
Server
1
2 3 4 5 6 70
COB-ID
ccd
Idx
2
Idx
1
Sidx
data
1
2 3 4 5 6 70
COB-ID
ccd
Idx
2
Idx
1
Sidx
data
data
data
data
data
read request
read response
43h
47h
4Bh
4Fh
40h
ccd=
ccd=
ccd=
ccd=
ccd=
Message type Data length used
4
bytes
3
bytes
2
bytes
1 byte
read request 40
h
40
h
40
h
40
h
Request read value
Read response 43
h
47
h
4B
h
4F
h
Return read value
Error response 80
h
80
h
80
h
80
h
Error