Chapter 10 CANopen Function and Operation
Response data:
PLC device
Message
Header
Message
data
D24004
D24005
D24006
Example 2: read the value of (Index_subindex) 212D_0 in slave of No. 3 through SDO; the data type of
(Index_subindex) 212D_0 is double words (32 bits).
Request data:
PLC device
D25000
Message
Header
D25001
D25002
D25003
Message
data
Main index high byte =21 Main index low byte =2D
D25004
D25005
10.4.2 Data Structure of NMT Message
Use the NMT service to manage the CANopen network such as start, operation, reset of nodes, etc.
The following table shows the data format of the NMT request message.
PLC device
Request message
High byte Low byte
D25000
Message
Header
ReqID Command (Fixed to 01)
D25001
Reserved Size (Fixed to 04)
D25002
Type (Fixed to 03) Node ID
D25003
Message
data
Reserved NMT service code
D25004
Reserved Node ID
Command: Fixed to 01.
ReqID: the request ID. Whenever an NMT request message is sent, the message is given a ReqID for
the CANopen master to identify. Before another NMT request message is sent out, the original ID
number must be changed. In other words, change the value of ReqID. The ReqID range is between
00–FF (Hex) to trigger sending the NMA request message.