9 | More about CANopen?
STÖBER
40
09/2019 | ID 442637.01
9.3.2.2
Segmented transfer
For a segmented transfer, data is split into segments. The total number of bytes to be transmitted are sent in what is called
a first initiate message ("Initiate SDO Download"); this is followed by the remaining segments ("Download SDO Segment"),
each with 7 bytes.
Initiate SDO Download Protocol
x
e
Byte
Bit
0
4...7
1...3
7...6
4
3...2
0
1
Master
Slave
ccs=1
n
s
m
d
x
Byte
Bit
0
4...7
1...3
7...5
4...0
scs=3
m
reserved
ccs
Client command specifier
1 = Initiate download request
scs
Server command specifier
3 = Initiate download response
n
Number of bytes
Number of bytes in "Data" that contain no usable data.
If e = 0 , s = 1, then n = valid, otherwise n = 0
e
Transfer type
§
0 = Normal transfer
§
1 = Expedited transfer
s
Size indicator
§
0 = Not displayed
§
1 = Displayed
m
Multiplexor
= Index + subindex
d
Data
§
If e = 0, s = 0, then d = reserved
§
If e = 0, s = 1, then d = number of bytes to be
transmitted
§
If e = 1, s = 1, then d = 4-n
x
Unused
x = 0