Delta AS Series - Data Structure of SDO Request Message

10.4 Sending SDO, NMT and Reading Emergency Message
through the Ladder Diagram
You can edit the request message mapping area to affect the transmission of SDO, NMT and Emergency
messages. The following table shows the corresponding relations between the request message mapping
area, response message mapping area, and PLC device.
PLC device
Mapping area
Mapping length
D25000-D25031
SDO request message, NMT service message and
Emergency request message
64 bytes
D24000-D24031
SDO response message and Emergency response message
64 bytes
The CANopen master can only send one SDO, NMT, or Emergency request message to the same device at a
time. Clear the request message mapping area to zero when sending SDO, NMT, or Emergency request
message through the WPL program.
10.4.1 Data Structure of SDO Request Message
Sending SDO through the ladder diagram reads or writes the slave parameter.
1. The data format of the SDO request message:
PLC device
Request message
High byte
Low byte
D25000
Message Header
ReqID
Command (Fixed to 01)
D25001 Reserved Size
D25002 Type Node ID
D25003
Message Data
High byte of main index Low byte of main index
D25004
Reserved Sub-index
D25005
Datum 1 Datum 0
D25006
Datum 3 Datum 2
D25007 - D25031 Reserved
 ReqID: the request ID. Whenever an SDO request message is sent out, the message is given a ReqID
for CANopen master to identify. When reading/writing another SDO message, the original ID number
must be changed. In other words, reading/writing SDO is triggered by changing of the value of
“ReqID”. The ReqID range is between 00–FF (Hex).
 Size: the length of the message data. The counting starts from D6253 with a byte as the unit. When
reading, it is fixed to four and when writing, it is four plus the byte number of data types of index and
subindex and the maximum value is eight. But when writing, if the data type of the index and subindex
is word, the data length is six. The data length is file if the data type is byte.
 Node ID: the node address for the target equipment on a CANopen network.
 Type: 01 indicates the read access; 02 indicates the write access.
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Call +1(800)985-6929 To Order or Order Online At Deltaacdrives.com