Add Variables to a Function Block Diagram

Each value that is read or written by your Function Block Diagram is represented by a variable or a constant. Constant values are values that are fixed and are described in Add a Constant Value to a Function Block Diagram. Variable values change according to the data that is stored in your system and the calculations that are performed on it.

There are 2 types of variable:

• Internal variables are values that are used by the program but are not written to an item in the database. For example, values that are used in a conversion.
• Direct variables are values that are stored in the database, for example, a point value.

The following sections explain how to add variables to your Function Block Diagram:

• Add a Direct Variable to a Function Block Diagram
• Add an Internal Variable to a Function Block Diagram.