BS EN IEC 61131-3-2025 PDF

Full title and description

STB BS EN IEC 61131-3-2025 — Programmable controllers — Part 3: Programming languages. This publication is the British adoption (BS EN IEC) of IEC 61131-3:2025 and defines the syntax, semantics and configuration elements for the unified suite of programming languages used for programmable controllers (PLCs), including Structured Text (ST), Ladder Diagram (LD), Function Block Diagram (FBD) and Sequential Function Chart (SFC).

Abstract

IEC 61131-3:2025 specifies a unified suite of programming languages for programmable controllers and adds or updates features compared with the previous edition (2013), notably inclusion of UTF‑8 strings and related functions, and an Annex documenting added, removed or deprecated features. The standard covers textual and graphical languages, program structuring (SFC), configuration elements for program installation and features that facilitate controller communication.

General information

• Status: Published (British adoption available as BS EN IEC 61131-3:2025).
• Publication date: IEC base publication: 22 May 2025; British adoption (BS EN IEC) publication/availability reported around 8 July 2025 (BSI catalogue entries).
• Publisher: International edition published by IEC (IEC webstore); British edition published and distributed by BSI as BS EN IEC 61131-3:2025.
• ICS / categories: 25.040.40 (Industrial process measurement and control); 35.240.50 / IT applications in industry (as listed on the IEC and national adoption records).
• Edition / version: Edition 4.0 (IEC 61131-3:2025, edition 4.0).
• Number of pages: IEC bilingual publication listed as 518 pages; national/BS adoption packaging shows ~258 pages for the BS EN IEC publication (formats and page counts vary between the IEC master text and national publishing formats).

Scope

This part of the IEC 61131 series standardizes the syntax and semantics of programming languages for programmable controllers and related configuration elements. It specifies the textual language Structured Text (ST) and graphical languages Ladder Diagram (LD) and Function Block Diagram (FBD), plus Sequential Function Chart (SFC) constructs for program structure, and includes features that support installation, communication and interoperability in automated systems. The 2025 edition introduces modernizations such as UTF‑8 string support and documents feature changes relative to the 2013 edition.

Key topics and requirements

• Definition of syntax and semantics for Structured Text (ST), Ladder Diagram (LD) and Function Block Diagram (FBD).
• Sequential Function Chart (SFC) elements for structuring programs and function blocks.
• Configuration elements supporting program installation into programmable controller systems.
• Communication-related features to facilitate interaction between controllers and other automation components.
• Support for UTF‑8 strings and associated functions (new in the 2025 edition).
• Annex B: comprehensive list of features added, removed or deprecated compared with IEC 61131-3:2013.

Typical use and users

Used by automation engineers, control systems designers, PLC/automation software developers, tool vendors (IDE/compilers for PLC languages), integrators and maintainers of industrial control systems. The standard is applied when developing, exchanging or verifying PLC programs and when implementing vendor tools to ensure portability and conformance across platforms.

Related standards

Part of the IEC 61131 series; see IEC 61131-1 for general definitions and architecture of programmable controllers and other related parts in the series. The 2025 edition of Part 3 replaces/succeeds the 2013 edition (IEC 61131-3:2013 / BS EN 61131-3:2013) in national libraries and catalogues following adoption.

Keywords

Programmable controllers, PLC, programming languages, Structured Text (ST), Ladder Diagram (LD), Function Block Diagram (FBD), Sequential Function Chart (SFC), UTF‑8 strings, configuration, IEC 61131, BS EN, automation.

FAQ

Q: What is this standard?

A: It is Part 3 of the IEC 61131 series — the international standard that specifies programming languages and related elements for programmable controllers; the referenced publication here is the 2025 edition adopted and published as BS EN IEC 61131-3:2025 for the UK.

Q: What does it cover?

A: The syntax and semantics of the unified suite of PLC languages (ST, LD, FBD), program structuring with SFC, configuration elements for installation, and features for controller communication. The 2025 edition adds UTF‑8 string support and documents feature-level changes versus the 2013 edition.

Q: Who typically uses it?

A: Automation and controls engineers, PLC programmers, tool and runtime vendors, system integrators and maintenance teams who need language definitions, portability guarantees and conformance criteria for PLC programs.

Q: Is it current or superseded?

A: As published in 2025 this edition is the current version of IEC 61131-3 and replaces the 2013 edition; national BS EN IEC editions (BSI publication) reflect the 2025 adoption and supersede BS EN 61131-3:2013. Publication and adoption dates vary by publisher/national body (IEC base publication 22 May 2025; BSI/national availability reported July 2025).

Q: Is it part of a series?

A: Yes — it is Part 3 of the IEC 61131 series (Programmable controllers). Other parts (for example IEC 61131-1) define general rules, architecture and requirements referenced by Part 3.

Q: What are the key keywords?

A: Structured Text (ST), Ladder Diagram (LD), Function Block Diagram (FBD), Sequential Function Chart (SFC), PLC, programmable controller, programming languages, UTF‑8, configuration, IEC 61131.