Danfoss FC 300 Manual page 19

FC 300 CANopen
- H o w t o C o n t r o l t h e F C 3 0 0 -
Basic structure of the CAN data telegram
Each communication object has a unique identity (COB-ID) comprising the function code and the node
ID.
COB identifier (COB-ID):
10 9 8
Function
PDOs represent real-time process data with high priority.
SDOs represent non-time-critical data and are used to configure the frequency converter.
NMT functions monitor the network stability and include synchronisation, detection of faults and
emergency message transmission.
Comparison of functionality of PDOs and SDOs:
Process Data Objects (PDO)
0-8 bytes of data
Represent process data
Consist of CAN ID and data
Represent real-time data of high priority
Broadcast unacknowledged on the bus, no
protocol overhead
Content is fixed by the CAN ID, configured
by the user.
Broadcast functions
NMT
SYNC
TIME STAMP
7 6
Node ID
Service Data Objects (SDO)
Client-Server communication
Always 8 bytes of data
If fewer than 8 bytes are used, the remainder of the
object is filled with 0's.
SDOs permit transmission of larger volumes of data by
segmentation.
Used to configure the device by accessing the Object
Directory (OD)
Non-time-critical data, of low priority
Always access the OD
Node functions
EMCY
PDO1 (write), PDO1 (read)
PDO2 (write), PDO2 (read)
PDO3 (write), PDO3 (read)
PDO4 (write), PDO4 (read)
SDO (write), SDO (read)
NMT Error Control
MG.33.J1.02 VER. 050301 – VLT is a registered Danfoss trademark
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