Introduction

Control Expert software enables you to create DFB user function blocks, using automation languages. A DFB is a program block that you write to meet the specific requirements of your application. It includes:

  • one or more sections written in Ladder (LD), Instruction List (IL), Structured Text (ST) or Functional Block Diagram (FBD) language

  • input/output parameters

  • public or private internal variables

Function blocks can be used to structure and optimize your application. They can be used whenever a program sequence is repeated several times in your application, or to set a standard programming operation (for example, an algorithm that controls a motor, incorporating local safety requirements).

By exporting then importing these blocks, they can be used by a group of programmers working on a single application or in different applications.

Benefits of Using a DFB

Using a DFB function block in an application enables you to:

  • simplify the design and entry of the program

  • increase the legibility of the program

  • facilitate the debugging of the application (all of the variables handled by the function block are identified on its interface)

  • reduce the volume of code generated (the code that corresponds to the DFB is only loaded once - however many calls are made to the DFB in the program, only the data corresponding to the instances are generated)

Comparison with a Subroutine

Compared to a subroutine, using a DFB makes it possible to:

  • set processing parameters more easily

  • use internal variables that are specific to the DFB and therefore independent from the application

  • test its operation independently from the application

Furthermore, LD and FBD languages provide a graphic view of the DFBs, facilitating the design and debugging of your program.

DFB Created with Previous Software Versions

DFBs created using PL7 and Concept must first be converted using the converters that come with the product, before being used in the application.

Domain of Use

The following table shows the domain of use for the DFBs.

Function

Domain

PLCs for which DFBs can be used.

Premium\Atrium and Quantum

DFB creation software

Control Expert

Software with which DFBs can be used.

Control Expert

Programming language for creating the DFB code.

IL, ST, LD or FBD (1)

Programming language with which DFBs can be used.

IL, ST, LD or FBD (1)

(1) IL: Instruction List , ST: Structured Text, LD: LaDder, FBD: Functional Block Diagram language.