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.
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 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.
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