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FS-8700-47 DNP 3.0 Driver Manual Page 37 of 51
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Appendix A.11. Controlling the DNP 3.0 Driver’s Qualifier
The protocol uses a qualifier in the application layer part of a message to indicate how data must be
packed in the message. The DNP 3.0 Driver as a Client will default to use a Qualifier of 1. The
qualifier is used internally by the driver and is of no concern unless the DNP protocol has been
implemented to require the use of qualifiers other then 1. In this case it is possible to change the
driver’s default value by specifying the dnpQualifier parameter. For example, to address a Control
Relay Output Descriptor object in a Multlin 489 Generator management relay, the vendor data sheet
indicates that only qualifiers 17 and 28 may be used.
When the driver is configured as a Server then the dnpQualifier parameter specified in the CSV file is
not used. The qualifier of the requesting poll is used in interpreting the request and forming the
response. The driver accepts poll’s that have the DNP qualifier set to 6 which effectively requests the
Server to send back all objects of the type requested. The driver’s support for this qualifier is limited
by the length of the response message. The response must fit in one 255 byte message. The
number of objects contained in the response message (and hence the length of the response) is
controlled by the length parameter. We have found lengths in the upper range 10 to 30 successful.
As a Server, if configured to serve ‘changed’ data the driver may choose the qualifier itself as the data
object may be non sequential. See 5.3.8.
Appendix A.12. FieldServer DNP Node Number
The FieldServer’s DNP node number is set in the CSV file. In the following example the node is set to
22.
FieldServer
Title ,System_Node_ID
B1 ,22