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IEC 61131 Basics

Presented by

Bill Lydon, Director PLCopen North America

Automation Industry Consultant

blydon@PLCopen-NA.org

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Why standard software?

Standardization Improves Productivity

Quality & Reliability

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Percentage of Software development costs in

production systems (source: McKinsey)

0%

20%

40%

60%

80%

100%

1970 1980 1990 2000

Mechanic Electric Software

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Software Functions Increasing Complexity Increases Exponentially

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“… the never ending story of software ”

enhancements…..

new requirements ...

new functionalities ….

new wishes ...

Typically software enhancements & maintenance cost are 2 times the initial development investment.

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Conceptual

Design Specification

Functional

Design

Verification

Coding Testing

Refining

Commissioning

Maintenance

Standard Software Advantages

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for efficiency in automation Standard Software Advantages

Improved Software Reliability – Common Design Architecture

Improved Productivity

Common Base of Understanding & Training

Improves Maintenance Efficiency • Emergency Bug Fixes & Corrective Bug Fixes

• Adding Features & Functions

• Mandatory Changes ( Law, Safety,...)

• Enhancements

• Studies show software maintainers spend about 50% their time

understanding the code.

Lifecycle Maintenance = 2 X Initial Development

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IEC 61131-3 - International Electrotechnical Commission (IEC)

Open Programmable Logic Controller Standard 1st published 1993 - 3rd edition published 2013

Defined application program development environment

Strong data typing for error prevention

1 Structuring Tool – Sequential Function Chart (SFC)

4 programming languages: 2 Textual & 2 Graphical

Program Organization - Program Structuring & Reuse

What is IEC 61131-3 ?

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IEC 61131-3 Strong Data Types

BOOLEAN

REAL

INTEGER

STRING

TIME

ARRAY

STRUCTURES

USER DEFINED

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Languages

Instruction List (IL)

Structured Text (ST)

Ladder Logic/Diagram (LD)

Function Block (FB)

Sequential Function Chart (SFC)

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A B C

-| |--|/|----------------( )---[Function[---

Ladder Diagram (LD)

Standardized set of relay ladder programming

symbols and terminology

• Electrical Flow

• Large base of users

• Boolean equations

• Function Blocks

• Easy rules

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for efficiency in automation Ladder Diagram (LD)

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LD A

AND B

ST C

• Single accumulator based execution model

• Low Level Programming

• One operation such as storing a value in the

accumulator register, is allowed per line

Instruction List (IL)

Single statements, or instructions, written and

executed in a line-by-line format.

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C:= A AND NOT B

If A = FALSE THEN ...

CASE Select OF ....

• High level language, block structured

• Syntax resembles PASCAL, C, C+

• Complex statements and nested instructions possible

• Support for • Iteration loops (REPEAT-UNTIL; WHILE-DO)

• Conditional execution (IF-THEN-ELSE; CASE)

• Functions (SQURT(); SIN())

Structured Text (ST)

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AND

A C

B

• Graphical Language

• Program elements appear as blocks to be

“wired” together

Function Block Diagram (FB)

Function Examples: ADD, SQRT, SIN, COS, AND, OR, CASE, etc.

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for efficiency in automation Function Block Diagram (FB)

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Inputs Outputs

Function Block • Explicit Data • Variables • Tag Names • Logic • Actions/Calculations

Self Contained Building Blocks

Function Block

Inherent Data Integrity Checks

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Inputs Outputs

Function Examples • AND, OR, XOR, GATE…

• PID, SELECT, LIMIT…

• SQUARE ROOT, COS…

• ADD, SUB, DIV, MUL…

Function Block

Self Contained Building Blocks

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for efficiency in automation Function Block

Inputs Outputs

Send/Receive Email Serve UP WEB Pages

Send Messages (SMS)

Send SOAP Messages

Send XML Messages

OPC UA Communication

PEER to PEER

Self Contained Building Blocks

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BUILD

YOUR OWN

FUNCTIONS

Function Block

Encapsulation

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Built from standard blocks ...

Inputs Outputs User Created

Object

Encapsulation

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Ladder Logic Instruction List Structured Text

Build your own function blocks

with Ladder Logic, Instruction

List, or Structured Text

Standardization

Reuse Tested Code

Easily Understood

Self Documenting

Password Protect

Inputs Outputs Your Own

Function Block

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for efficiency in automation Sequential Function Chart (SFC)

Step 1

Transition

Step 2

Transition

Action 1

Action 2

Action 1

• Sequential Controls

• Procedural Controls

• Structured

• Describes Process

• Logic Driven

• Partition Control Functions

• Rapid Visual Diagnostics

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• Serial & Parallel Processes

• Process Synchronization

• Application examples • Startup Sequences

• Shutdown Sequences

• Presses

• Productions Lines

• Process Automation

• Packaging technology

• Machine tools

• Batch Process Control – S88

• Flexible Manufacturing

Sequential Function Chart (SFC)

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• Multiple Automation and Control Disciplines

• Process Design

• Logic Simulation

• Automatic Documentation

• Engineering Tools • Online Debug Environment

• Breakpoints

• Watch Windows

• Strip chart Recorder

• Integrated HMI

IDE - Integrated Design Environment (IDE)

IEC 61131 Controller

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Vendor Independent, Not for Profit Organization

Extends IEC 61131-3 Functionality

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More Information... www.PLCopen.org

Electronic Newsletter

Application Examples

Specifications

Compliant Products

Bill Lydon, Director PLCopen North America

Automation Industry Consultant

blydon@PLCopen-NA.org

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