Echelon SmartServer 2.2 - Manual (Page 447)

448 Using Analog Functional Blocks
Analog Functional Block Overview
The SmartServer includes an Analog Functional Block that you can use to perform mathematical or
logical operations on a set of input points and store the result in a specified output point. The Analog
Functional Block will then perform the specified operation each time any of the input points are
updated or at a specific interval.
You can select any scalar data point (data point with a single field) or the field of structured data point
as an input point. After you select the input points, you specify whether the Analog Functional Block
performs a mathematical or logical function on the input points. You can select a mathematical
operation to determine the minimum, maximum, average, or sum of two or more input points. The
calculated data point value is then written to the output point you specify (provided that it does not
exceed or go below the maximum and minimum values you specify). For example, consider a case in
which three SNVT_temp_f input points with values of 68, 72.5, and 78 are selected and a
mathematical function is selected and set to Average. The value sent to the output point is 72.83 (the
sum of the data points [218.5] divided by the number of input points [3]), provided that it does not
exceed or go below the specified maximum or minimum values.
You can use select a logical operation to compare the value of one or more input points to that of a
compare point, which can be another data point or a constant value. The Analog Functional Block
evaluates whether one, all, or a percentage of the input points are equal, not equal, less than, less than
or equal, greater than, or greater than or equal to the compare point based on the logical and output
functions you select. The result of the logical operation (TRUE or FALSE) is to the output point you
specify. For example, consider a case in which five input points are selected, a logical function is
selected and set to Greater Than, and three of the data points are actually greater than the compare
point:

If the output function is set to And, which means all the selected data points must be greater than
the compare point to return a TRUE value, the result of the logical function is FALSE.

If the output function is set to Or, which means that only one of the selected data points needs to
be greater than the compare point to return a TRUE value, the result of the logical function is
TRUE.

If the output function is set to Majority and the specified percentage is 50%, which means that at
least half of the selected data points needs to be greater than the compare point to return a TRUE
value, the result of the logical function is TRUE as 60% of the data points are greater than the
compare point.
After you select and configure a mathematical or logical operation, you select an output point. If the
Analog Functional Block is performing a mathematical operation, you can select a scalar data point
with the same type as the selected input points as the output point. If the Analog Functional Block is
performing a logical operation, you must select a SNVT_switch data point as the output point. You
can use the result stored in the output point to control one or more actuator devices.
You can create up to 20 Analog Functional Blocks per SmartServer if you are using the default
SmartServer v12 static interface. You can add more than 20 Analog Functional Blocks if you activate
the v40 dynamic interface, which features a dynamic external interface, on your SmartServer. See
Activating the SmartServer V40 XIF in Chapter 3, Configuring and Managing the SmartServer, for
more information on loading the V40 interface on the SmartServer.
Creating an Analog Functional Block
To create an analog functional block, do the following:
1. Open an Analog Functional Block application.
2. Select input points, which can include scalar data points or the individual fields of structured data
points. If you are performing a mathematical operation select two or more input points; if you are
performing a logical operation select one or more input points and a compare point.