Echelon i.LON 100 e2 Internet Server - Manual (Page 146)

i. LON 100 Internet Server Programmer’s Reference 9-9
Property Description
<Point> You can specify as many input data points as you want per Analog
Function Block. The input data points for an Analog Function Block are
defined by a list of <Point> elements in the <Data> parameter supplied to
the function.
For each element, you must specify an index number to be used within the
Analog Function Block (UCPTindex), the name of the data point
(UCPTpointName), and the interval to use when polling the data point’s
value (UCPTpollRate). The poll rate must be specified as an integer
between 0-6553. If the input data point is a structure, you must also
specify the name of the field to use when performing comparisons with the
data point (UCPTfieldName).
The value of the selected field for each input data point will be used to
generate a value for the output data point. This value assigned to the
output data point will vary, depending on the output function
(UCPToutputFunction) selected for the Analog Function Block.
NOTE: You should note that other
i. LON 100 applications may cause the
Data Server to poll this data point’s value as well. The poll rate specified
by these applications should be compatible with each other. For example, if
an Analog Function Block is polling a data point every 15 seconds, and the
Data Logger is polling that data point every 10 seconds, then the Data
Server will have to poll the value of the data point every five seconds to
ensure that each application gets a current value for each poll.
It is important to note this as you set poll rates for various applications, as
you may end up causing more polls than is efficient on your network. For
example, if an Analog Function Block is polling a data point every 9
seconds and a Data Logger is polling a data point every 10 seconds, the
Data Server would have to poll the data point every second to ensure that
each application polls for a current value. This may create a significant
amount of undesired traffic.
<CompareDataPoint> This element defines the compare data point this Analog Function Block
will use.
You must specify the name of the data point (UCPTpointName), the name
of the field to use when making comparisons with the data point
(UCPTfieldName) if it is a structure, and the interval to use when polling
the data point’s value (UCPTpollRate).
The value of this data point will be compared to the value of each input
data point when the output function selected for the Analog Function Block
is FN_COMPARE, FN_AND or FN_OR. The comparison to perform is
determined by the <UCPTcompFunction> property, and the result of this
comparison will be stored in the output data point.
This value will not be used in comparisons if the <UCPTtrueThreshold>
property is defined.