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6
DNP3 points and
controls
Point mapping
RCU database digital and analog inputs can
be configured to suit the SCADA master
needs in a number of ways:
RCU database points can be mapped to
specific DNP3 point indices.
RCU database points can be unmapped,
in which case they will not appear in the
DNP3 point indices and will not be
available to the SCADA system.
For mapped points, the DNP3 class can
be set as described below.
Point mapping is especially useful when
trying to reduce the bandwidth
requirements over the SCADA network by
removing points that are deemed
unnecessary. This can be achieved by
mapping all required points to contiguous
DNP3 indices starting at index 0. Unwanted
points can then be left unmapped (i.e., not
mapped to any class), in which case they
will not be returned by integrity poll or
individual poll or will they generate
unsolicited messages.
Note that all point configuration is carried
out with the RCU Connect PC utility.
Class assignment
For all mapped points, the user can assign
DNP3 class 0, 1, 2, 3 or "None."
Points with class "None" will not be returned
in an integrity poll. However, these points
can still be read by polling the specific data
type/point index for that point.
The advantage of setting class "None" is that
a point can still be scanned if required but
will not cause use of bandwidth in integrity
polls. The disadvantage is the potential
fragmentation of integrity polls.
Contiguous DNP3 indices
A DNP3 integrity poll will return all DNP3
points that have been mapped to the RCU
internal database and that have been
assigned to class 0, 1, 2 or 3. If the DNP3
mapping has gaps in the sequence of
indices caused either by an unmapped DNP3
index or by a mapped point being set to
class "None," it will result in multiple DNP3
fragments being sent across the SCADA
network. This problem can be avoided by
mapping the class "None" points to the end
of the DNP3 index.
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