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IEC 6-1131-3

The IEC (International Electrotechnical Commission) 6-1131-3 Standard is a widely recognized international standard for the programming of a PLC.

How many ‘Graphical languages’ are there in the IEC  6-1131-3  ?

a.  2

b.  3

c.  4

d.  5

The correct answer is A.
They are Ladder Diagram (LD) and  Function Block Diagram (FBD).

Ladder Diagram


Function Block Diagram


Programming Languages

1. Graphical

1. Ladder Diagram (LD)

2. Function Block Diagram(FBD)


2. Textual

1. Instruction List (IL)

2. Structured Text (ST)


3. Program Control Flow

1. Sequential Function Charts (SFC)

Sequential Function Charts are considered by many to be a graphical language.

IEC 61131-3 is the third part of the IEC 61131 family. This consists of:

•Part 1: General Overview

•Part 2 Hardware

•Part 3 Programming Languages

•Part 4 User Guidelines

•Part 5 Communication

•Part 7 Fuzzy Logic

• Part 8 Application Guidelines


  • Standard will provide greater uniformity between PLCs
  • Does for the process world what OPC (OLE2) did for the computer world
  • Reuse work
  • Reduce amount of retraining
  • Enables programmers to integrate multiple languages within the same application
  • Does not…–
    Specify physical I/O–
    Memory  address mapping
Mark Weisner
Mark Weisner
Mark Weisner is a technical specialist at ISA.

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