June 2009

Module 9FBD Language

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Function Block Diagram (FBD) is a graphical language that is data flow oriented

Complies with IEC 61131-3 standard

Particularly suitable for continuous or discrete control applications

FBD program uses functions and instances of function blocks linked each other by links or intermediate variables. Comments can be add to describe the logic of program

FBD programming is not cell oriented but a grid help you to position the blocks

Overview

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Execution numberExecution sequence is defined by the position of FFBs and links but can be changed

Free form editor

Based on a customizable grid (by default 36 columns x 24 rows)

FBD Editor

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Data selection

FFB input assistant

Call subroutine block

LinkToggle pin negation

Jump

Jump label

Return

Comment

FBD Toolbar

Types library browser

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Select a FFB1. Activate data

selection 2. Access to FFB

selection

3. Choose the library

4. Access to FFB types or instances

5. Choose the FFB

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Select FFB type

Use FFB Input Assistant

Select or change FFB instance name

For each connected pin enter or select a

variable or value

Access FFB online help

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Insert a FFB by Drag and Drop

Select the funtion block (library / family / block)

Drag and drop the function block to the

FBD editor

Access the Types Library Browser

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VariablesDirectly enteredDefine through the data selector or by drag and drop from the data editor

FFBsDefine through the data selector or by drag and drop from the <Libset> browserDefine through the FFB input assistant

LoopsLinks are not permitted to create a loopUse intermediate (feedback) variable to resolve a loop

Link of string variablesPins of type string cannot be link together (FFB output to another FFB input)Use intermediate variable to resolve a string link

Programming Rules

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Extendable Blocks

Some function blocks can be extended up to 32 pins

by making a grab of its bottom part

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Execution SequenceExecution sequence is determined by

the position of the FFBs (executed from left to right and from top to bottom)

If FFBs are linked graphically the execution sequence is determined by the signal flow

The execution sequence is indicated for each FFB by the execution number (if the top right corner of the frame)

To change the execution order suggested by the system

Change the FFBs positionModify the links between FFBsModify the execution number of some

FFBs