Specifications

4.2 POUs

4.2.4 Function blocks

4-7

PROGRAM

CONFIGURATION

4.2.4 Function blocks

Functions, function blocks, and operators are used to edit function blocks.

Function blocks can be used by calling them from programs or function blocks. Note that they

cannot be called from functions.

Function blocks can retain the input status since they can store values in internal and output

variables. Since they use retained values for the next processing, they do not always output the

same results even with the same input values.

Function blocks can be described in the ST or structured ladder/FBD language.

● Instantiation

Function blocks need to be instantiated to be used in programs.

For details of instantiation, refer to the following section.

Section 4.2.8 Functions and function blocks

Instances are variables representing devices assigned to labels of function

blocks.

Devices are automatically assigned when instances are created with local labels.

4.2.5 Operators

Operators can be used by calling them from programs, functions, or function blocks.

Operators cannot be edited.

Operators always output same processing results for the same input values.

Function block

Operator

Function block

Function