IEC 61131-3-2013 PDF

Full title and description

IEC 61131-3:2013 — Programmable controllers — Part 3: Programming languages. This edition (Edition 3.0) defines the syntax, semantics and programming model for a unified suite of programming languages used for programmable controllers (PLCs), together with structuring elements, data types, namespace and object-oriented extensions introduced as a compatible extension to the 2003 edition.

Abstract

IEC 61131-3:2013 specifies a set of standard programming languages and program organization concepts for programmable controllers. The document standardizes two textual languages (Structured Text — ST and Instruction List — IL) and two primary graphical languages (Ladder Diagram — LD and Function Block Diagram — FBD), and defines Sequential Function Chart (SFC) elements for program structuring. The 2013 edition extends the previous edition with new data types and conversion functions, references and namespaces, and object‑oriented features for function blocks and classes. (Note: this edition was later superseded by IEC 61131-3:2025.)

General information

• Status: Withdrawn / Replaced by IEC 61131-3:2025 (published 22 May 2025).
• Publication date: 20 February 2013.
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: 25.040.40; 35.240.50.
• Edition / version: Edition 3.0 (2013).
• Number of pages: 464 (as published by IEC).

Scope

The standard specifies syntax and semantics for a unified suite of programming languages for programmable controllers and defines program organization units (POUs), variable and type definitions, standard library functions, and elements for configuration and deployment into PLC systems. It provides rules for data types, conversions, references and namespaces, and introduces object-oriented features (classes and object-oriented function blocks) to improve modularity and reuse. IEC 61131-3:2013 is intended to improve portability, maintainability and clarity of control software across vendors and projects.

Key topics and requirements

• Definition of programming languages: Structured Text (ST), Instruction List (IL — marked deprecated in this edition), Ladder Diagram (LD), Function Block Diagram (FBD).
• Sequential Function Chart (SFC) elements for organizing sequential and parallel control flows (structuring tool, not a standalone textual language).
• Program Organization Units (POUs): programs, functions and function blocks; formal interfaces and instantiation rules.
• Data types and conversion functions — new/extended types introduced in the 2013 edition.
• References, name spaces and scoping rules to reduce ambiguity and enable larger applications.
• Object‑oriented extensions: classes and object‑oriented function blocks for encapsulation and reuse.
• Standard library definitions and requirements for deterministic execution semantics appropriate for real‑time control.
• Guidance for implementation conformance levels and interoperability considerations for tool vendors and runtime implementers.

Typical use and users

IEC 61131-3:2013 is used by automation and control engineers, PLC programmers, system integrators, tool and runtime vendors, test and validation teams, and educators. It is applied when developing, exchanging or maintaining PLC control software for manufacturing automation, process control, building automation, water/wastewater systems, energy and transportation controls where standardized, portable and maintainable control code is required.

Related standards

Commonly referenced companion standards and work include: IEC 61131-1 (general information and definitions for programmable controllers), IEC 61131-2 (equipment requirements and test procedures), IEC 61131-4 (user guidelines for programming languages), IEC 61499 (function blocks for distributed systems), and industry consortia outputs such as PLCopen specifications and mappings between IEC 61131-3 and information models (e.g. OPC UA mappings).

Keywords

IEC 61131-3, PLC programming, programmable controllers, Structured Text (ST), Instruction List (IL), Ladder Diagram (LD), Function Block Diagram (FBD), Sequential Function Chart (SFC), Program Organization Unit (POU), object-oriented function blocks, namespaces, data types, automation standard.

FAQ

Q: What is this standard?

A: IEC 61131-3:2013 is the third part of the IEC 61131 series, specifying programming languages and program organization for programmable controllers (PLCs). It formalizes language syntax, semantics, data types and modular structures used in industrial control software.

Q: What does it cover?

A: It covers standardized programming languages (ST, IL, LD, FBD), SFC structuring elements, POUs (programs, functions, function blocks), data types and conversions, references and namespaces, standard libraries, and object‑oriented extensions introduced in the 2013 edition.

Q: Who typically uses it?

A: PLC programmers, automation engineers, system integrators, tool vendors (editors, compilers, runtimes), validation and compliance teams, and educators teaching industrial control programming.

Q: Is it current or superseded?

A: IEC 61131-3:2013 was published on 20 February 2013. It was superseded and withdrawn when IEC 61131-3:2025 (Edition 4.0) was published on 22 May 2025. For new projects and for feature lists (additions, deprecations and removals) consult the 2025 edition.

Q: Is it part of a series?

A: Yes. IEC 61131-3 is Part 3 of the IEC 61131 series of standards for programmable controllers; other parts (for example IEC 61131-1 and IEC 61131-2) cover general definitions and equipment requirements.

Q: What are the key keywords?

A: PLC, programmable controller, Structured Text, Ladder Diagram, Function Block Diagram, Sequential Function Chart, program organization unit, object-oriented function block, namespaces, IEC 61131.