Programs and Calculations

Introduction

Certain tag types allow you to define a calculation or program. For example, the value of a Calculated Analog Data Point Tag is defined using an IEC 61131-3 Expression.

The configuration tool provides a Text Editor to edit calculations and programs.

To edit a calculation, right-click the calculation tag in the Tag Window, and then click Edit Calculation.
To edit a program, right-click the Program Tag in the Tag Window, and then click Edit SourceCode.

A program in the text editor:

Finding and Correcting Code Errors

When you save a program or calculation, Fernhill SCADA will compile the code. If there are no errors, the program or calculation will start immediately. Any errors will be reported in the Status Monitor Window:

Tag status window showing a program error

Errors in the code are highlighted using a dotted red underline. For example "CalculatedValues" is underlined showing the location of the error:

Program error shown with dotted red underline

Moving the cursor over the error will display a tooltip window giving more detail of the error:

Watch Program Variables

You can watch program variables as the program executes:

To open the Global Variables Dialog:

Right-click anywhere in the text editor window.
Select Watch global variables.

Further Information

Text Editor Commands

For information about the commands supported by the text editor.

Fernhill SCADA Configuration Tool

To learn about the Fernhill SCADA Configuration Tool.

Glossary

For the meaning of terms used in Fernhill SCADA.