EN IEC 61131-3:2025

Programmable controllers - Part 3: Programming languages

IEC 61131-3:2025 specifies the syntax and semantics of programming languages for programmable controllers as defined in IEC 61131-1. This document specifies the syntax and semantics of a unified suite of programming languages for programmable controllers (PCs). This suite consists of the textual language structured text (ST), and the graphical languages, ladder diagram (LD) and function block diagram (FBD). An additional set of graphical and equivalent textual elements named sequential function chart (SFC) is defined for structuring the internal organization of programs and function blocks. Also, configuration elements are defined which support the installation of programmable controller programs into programmable controller systems. In addition, features are defined which facilitate communication among programmable controllers and other components of automated systems. This edition includes the following significant technical changes with respect to the previous edition: a) inclusion of UTF-8 strings and their associated functions; b) Annex B contains a comprehensive list of features that have been added, removed or deprecated in comparison to IEC 61131-3:2013.

Speicherprogrammierbare Steuerungen - Teil 3: Programmiersprachen

Automates programmables - Partie 3: Langages de programmation

IEC 61131-3: 2025 spécifie la syntaxe et la sémantique des langages de programmation utilisés pour les automates programmables tels que définis dans l’IEC 61131-1. Le présent document spécifie la syntaxe et la sémantique d’une suite unifiée de langages de programmation utilisés pour les automates programmables (AP). Cette suite est constituée du langage textuel ST (Structured Text) et des langages graphiques LD (Ladder Diagram) et FBD (Function Block Diagram). Un autre ensemble d’éléments graphiques et textuels équivalents appelé SFC (Sequential Function Chart) est défini pour structurer l’organisation interne des programmes et des blocs fonctionnels. Des éléments de configuration qui prennent en charge l’installation des programmes pour automate programmable dans des systèmes d’automate programmable, sont également définis. De plus, des caractéristiques sont définies pour faciliter la communication entre les automates programmables et les autres composants des systèmes automatisés. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente: a) inclusion des chaînes UTF-8 et de leurs fonctions associées; b) l’Annexe B contient une liste complète des fonctionnalités qui ont été ajoutées, supprimées ou déconseillées par rapport à l’IEC 61131-3:2013.

Programirljivi krmilniki - 3. del: Programski jeziki

General Information

• Status: Published
• Publication Date: 03-Jul-2025
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.240.50 - IT applications in industry
• Technical Committee: CLC/TC 65X - Industrial-process measurement, control and automation
• Drafting Committee: IEC/SC 65B - IEC_SC_65B
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 04-Jul-2025
• Due Date: 30-Jul-2024
• Completion Date: 04-Jul-2025
• Ref Project: SIST EN IEC 61131-3:2025 - Programmable controllers - Part 3: Programming languages

Relations

• Replaces: EN 61131-3:2013 - Programmable controllers - Part 3: Programming languages
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2025
Programirljivi krmilniki - 3. del: Programski jeziki
Programmable controllers - Part 3: Programming languages
Speicherprogrammierbare Steuerungen - Teil 3: Programmiersprachen
Automates programmables - Partie 3: Langages de programmation
Ta slovenski standard je istoveten z: EN IEC 61131-3:2025
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.240.50 Uporabniške rešitve IT v IT applications in industry
industriji
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61131-3

NORME EUROPÉENNE
EUROPÄISCHE NORM July 2025
ICS 25.040.40; 35.240.50 Supersedes EN 61131-3:2013
English Version
Programmable controllers - Part 3: Programming languages
(IEC 61131-3:2025)
Automates programmables - Partie 3: Langages de Speicherprogrammierbare Steuerungen - Teil 3:
programmation Programmiersprachen
(IEC 61131-3:2025) (IEC 61131-3:2025)
This European Standard was approved by CENELEC on 2025-06-26. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61131-3:2025 E

European foreword
The text of document 65B/1281/FDIS, future edition 4 of IEC 61131-3, prepared by SC 65B
"Measurement and control devices" of IEC/TC 65 "Industrial-process measurement, control and
automation" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-07-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-07-31
document have to be withdrawn
This document supersedes EN 61131-3:2013 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61131-3:2025 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60848 NOTE Approved as EN 60848
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 61131-1 - Programmable controllers - Part 1: General EN 61131-1 -
information
IEC 61131-5 - Programmable controllers - Part 5: Communications EN 61131-5 -
ISO/IEC 10646 - Information technology - Universal coded character - -
set (UCS)
ISO/IEC 60559 - Information technology - Microprocessor Systems - - -
Floating-Point arithmetic
IEC 61131-3 ®
Edition 4.0 2025-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Programmable controllers –
Part 3: Programming languages
Automates programmables –
Partie 3: Langages de programmation
ICS 25.040.40, 35.240.50 ISBN 978-2-8327-0436-3

IEC 61131-3:2025-05(en-fr)
– 2 – IEC 61131-3:2025 © IEC 2025
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
4 Architectural models . 17
4.1 Software model . 17
4.2 Communication model . 19
4.3 Programming model . 20
5 Compliance . 22
5.1 General . 22
5.2 Feature tables . 22
5.3 Implementer’s compliance statement . 22
6 Common elements . 24
6.1 Use of printed characters . 24
6.1.1 Character set. 24
6.1.2 Identifiers . 24
6.1.3 Keywords . 25
6.1.4 Use of white space . 25
6.1.5 Comments . 25
6.2 Pragma. 26
6.3 Literals – External representation of data . 26
6.3.1 General. 26
6.3.2 Numeric literals and string literals . 26
6.3.3 Character string literals . 28
6.3.4 Duration literal . 31
6.3.5 Date and time of day literal . 31
6.4 Data types . 32
6.4.1 General. 32
6.4.2 Elementary data types (BOOL, INT, REAL, STRING, etc.) . 32
6.4.3 Generic data types . 36
6.4.4 User-defined data types . 37
6.5 Variables . 51
6.5.1 Declaration and initialization of variables . 51
6.5.2 Variable sections . 54
6.5.3 Variable length ARRAY variables . 57
6.5.4 Constant variables . 59
6.5.5 Directly represented variables ( % ) . 59
6.5.6 Retentive variables (RETAIN, NON_RETAIN) . 62
6.6 Program organization units (POUs) . 63
6.6.1 Common features for POUs . 63
6.6.2 Functions . 77
6.6.3 Function blocks. 113
6.6.4 Programs . 132
6.6.5 Classes. 134
6.6.6 Interface . 155
6.6.7 Object-oriented features for function block types . 165

IEC 61131-3:2025 © IEC 2025 – 3 –
6.6.8 Polymorphism . 171
6.7 Sequential function chart (SFC) elements. 174
6.7.1 General. 174
6.7.2 Steps . 175
6.7.3 Transitions . 176
6.7.4 Actions . 179
6.7.5 Rules of evolution . 187
6.8 Configuration elements . 195
6.8.1 General. 195
6.8.2 Tasks . 200
6.9 Synchronization of concurrent execution . 205
6.9.1 General. 205
6.9.2 Mutex . 206
6.9.3 Object-oriented mutex . 208
6.9.4 Semaphore. 209
6.9.5 Object-oriented semaphore . 211
6.10 Namespaces . 211
6.10.1 General. 211
6.10.2 Declaration . 212
6.10.3 Usage . 217
6.10.4 Namespace directive USING . 218
7 Textual languages . 221
7.1 Common elements . 221
7.2 Structured text (ST) . 221
7.2.1 General. 221
7.2.2 Expressions . 221
7.2.3 Statements . 223
8 Graphical languages . 229
8.1 Common elements . 229
8.1.1 General. 229
8.1.2 Representation of variables and instances . 229
8.1.3 Representation of lines a
...