WG 7 - TC 65/SC 65B/WG 7

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.

IEC TR 61131-8:2017(E) applies to the programming of program­mable controller systems using the programming languages defined in IEC 61131-3. The scope of IEC 61131-3 is applicable to this part.
This document provides
a) guidelines for the application of IEC 61131-3,
b) guidelines for the implementation of IEC 61131-3 languages for programmable controller systems,
c) programming and debugging tool (PADT) recommendations.
For further information see IEC 61131-4 which describes other aspects of the application of programmable controller systems, e.g. electromagnetic compatibility or functional safety. This third edition cancels and replaces the second edition published in 2003. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: This third edition is a compatible extension of the second edition. The main extensions are new data types and conversion functions, references, name spaces and the object oriented features of classes and function blocks (see listing in Annex B of IEC 61131-3:2013).

IEC 61131-2:2017 specifies functional and electromagnetic compatibility requirements and related verification tests for any product where the primary purpose is performing the function of industrial control equipment, including PLC and/or PAC, and/or their associated peripherals which have as their intended use the control and command of machines, automated manufacturing and industrial processes, e.g. discrete, batch and continuous control.
This fourth edition cancels and replaces the third edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) removal of safety requirements and instead pointing to IEC 61010-2-201;
b) addition of negative logic digital inputs and outputs;
c) addition of Type 3-d digital input;
d) addition of 2,7 GHz to 6 GHz requirement for Radio-frequency electro-magnetic amplitude modulated immunity;
e) clarification of temperature testing;
f) clarification of type testing;
g) deprecation of certain technologies;
h) general update of multiple aspects of functionality and EMC;
i) reorganization of clauses to associate requirements and verifications more closely.

IEC 61131-9:2013 specifies a single-drop digital communication interface technology for small sensors and actuators SDCI (commonly known as IO-Link), which extends the traditional digital input and digital output interfaces as defined in IEC 61131-2 towards a point-to-point communication link. This technology enables the transfer of parameters to Devices and the delivery of diagnostic information from the Devices to the automation system.

IEC 61131-3:2013 specifies the syntax and semantics of a unified suite of programming languages for programmable controllers (PCs). This suite consists of two textual languages, Instruction List (IL) and Structured Text (ST), and two graphical languages, Ladder Diagram (LD) and Function Block Diagram (FBD). This third edition cancels and replaces the second edition, published in 2003 and constitutes a technical revision. It includes the following significant technical changes: It is a compatible extension of the second edition. The main extensions are new data types and conversion functions, references, name spaces and the object oriented features of classes and function blocks.

IEC 61131-6:2012 specifies requirements for programmable controllers (PLCs) and their associated peripherals, as defined in Part 1, which are intended to be used as the logic subsystem of an electrical/electronic/programmable electronic (E/E/PE) safety-related system. A programmable controller and its associated peripherals complying with the requirements of this part is considered suitable for use in an E/E/PE safety-related system and is identified as a functional safety programmable logic controller (FS-PLC). An FS-PLC is generally a hardware (HW) / software (SW) subsystem. An FS-PLC may also include software elements, for example predefined function blocks.

IEC 61131-2:2007 specifies requirements and related tests for programmable controllers (PLCs) and their associated peripherals (for example, programming and debugging tools (PADTs), human-machine interfaces (HMIs), etc.) which have as their intended use the control and command of machines and industrial processes. It establishes the definitions and identifies the principal characteristics relevant to the selection and application of PLCs and their associated peripherals. It specifies the minimum requirements for functional, electrical, mechanical, environmental and construction characteristics, service conditions, safety, EMC, user programming and tests applicable to PLCs and the associated peripherals. This third edition of IEC 61131-2 cancels and replaces the second edition published in 2003 and constitutes a technical revision. This third edition includes the following technical changes:
- Correction of the tests of Clause 6 and 9;
- Change of EMC requirements in Clause 8;
- New organization of Clause 11. This bilingual version (2012-05) corresponds to the monolingual English version, published in 2007-07.

introduces the end-users of Programmable Controller (PLC) to the IEC 61131 series, and to assist the end-users in their selection and specification of their PLC equipment according to the IEC 61131 series. This user guideline has as its main audience PLC end-users.

applies to the programming of program-mable controller systems using the programming languages defined in IEC 61131-3. It also provides guidelines for the implementation of these languages in programmable controller systems and their programming support environments (PSEs).

IEC 61131-1:2003 applies to programmable controllers (PLC) and their associated peri-pherals such as programming and debugging tools (PADTs), human-machine interfaces (HMIs), etc., which have as their intended use the control and command of machines and industrial processes. It gives the definitions of terms used in this standard. It identifies the principal functional characteristics of programmable controller systems. This second edition cancels and replaces the first edition published in 1992 and constitutes a technical revision. This bilingual version (2012-05) corresponds to the monolingual English version, published in 2003-05.

Specifies requirements and related tests for programmable controllers (PLC) and their associated peripherals (for example, programming and debugging tools (PADTs), human-machine interfaces (HMIs), etc.) which have as their intended use the control and command of machines and industrial processes.The object is to establish the definitions and identify the principal characteristics relevant to the selection and application of PLCs and their associated peripherals and to specify the minimum requirements for functional, electrical, mechanical, environmental and construction characteristics, service conditions, safety, EMC, user programming and tests applicable to PLCs and the associated peripherals.

IEC 61131-3:2003 specifies syntax and semantics of programming languages for programmable controllers as defined in part 1 of IEC 61131. This second edition of IEC 61131-3 cancels and replaces the first edition, published in 1993, and constitutes a technical revision. This bilingual version (2015-06) corresponds to the English version, published in 2003-01.

IEC 61131-5:2000 specifies communication aspects of a programmable controller. It specifies from the viewpoint of a PC how any device can communicate with a PC as a server and how a PC can communicate with any device. In particular, it specifies the behavior of the PC as it provides services on behalf of other devices and the services the PC application program can request from other devices. This bilingual version (2012-08) corresponds to the monolingual English version, published in 2000-11.
This publication is to be read in conjunction with the IEC 61131 series.

Defines a language for the programming of Fuzzy Control applications used by programmable controllers.

Programming of programmable controller systems using the programming languages defined in IEC 61131-3.