IEC 61131-3

IEC 61131-3
Title	IEC 61131-3
Status	Published
Year	1993
Version	3rd Edition
Publisher	International Electrotechnical Commission
Domain	Industrial automation

IEC 61131-3 IEC 61131-3 is the part of an international standard that defines programmable logic controller programming languages and programming model conventions for industrial automation, linking formal language definitions with practical implementation guidance from prominent organizations. It provides a framework for languages, data types, program structure, configuration models, debugging, and conformance testing used across major automation vendors and academic institutions. The standard plays a central role in integrating programmable logic controllers with systems developed by manufacturers, certification bodies, and research centers.

Overview

IEC 61131-3 specifies five programming languages and a common set of elements for editors, compilers, and runtime environments used by vendors such as Siemens, Schneider Electric, Rockwell Automation, ABB, and Mitsubishi Electric. The document defines program organization units, global and local variables, function blocks, and type systems that align with testing methodologies used by Underwriters Laboratories and TÜV Rheinland. It serves as a bridge between control hardware platforms produced by companies like Beckhoff and research initiatives at institutions such as ETH Zurich and Massachusetts Institute of Technology.

History and Development

The development of IEC 61131-3 involved committees within the International Electrotechnical Commission and contributions from industrial members including General Electric, Honeywell, Omron, and national committees from Germany, France, United States, and Japan. Early versions drew on concepts from work on programmable logic begun at companies like Allen-Bradley and standards efforts exemplified by ISO and IEC technical committees. Revisions responded to evolving needs from automation projects in sectors influenced by firms such as Siemens and research programs at Fraunhofer Society and CSRIO. The standard has been updated periodically to reflect changes in embedded systems architectures used by manufacturers like Intel and ARM Holdings.

Programming Languages and Syntax

The standard defines five languages: Instruction List (IL), Structured Text (ST), Ladder Diagram (LD), Function Block Diagram (FBD), and Sequential Function Chart (SFC), with syntax and semantics intended for use across products from Siemens, Rockwell Automation, and Schneider Electric. IL resembles assembly-level constructs used on processors from Intel and ARM Holdings; ST parallels high-level languages similar to Pascal and Ada used in projects at ETH Zurich and Massachusetts Institute of Technology. LD traces its heritage to relay logic practices employed by companies such as General Electric and Omron, while FBD and SFC align with graphical modeling approaches found in work by National Instruments and standards activity involving ISO. The standard also documents common function block interfaces used by automation libraries from Phoenix Contact and Beckhoff.

Configuration and Organization of Devices

IEC 61131-3 prescribes program organization units (POUs), tasks, resources, and configurations to describe how controller code maps to hardware produced by vendors like Siemens, Mitsubishi Electric, and ABB. The configuration model supports distribution across modules similar to architectures used in systems by Beckhoff and Schneider Electric, and interfaces with fieldbus technologies promoted by organizations such as the Fieldbus Foundation and PROFIBUS. The arrangement of libraries and repositories reflects asset management practices adopted by utilities and manufacturers including General Electric and Siemens Energy, and is compatible with lifecycle tools developed by Siemens Digital Industries Software and Rockwell Automation.

Data Types, Variables, and Memory Models

The standard defines elementary data types and derived types, arrays, and structures used in implementations by vendors such as Schneider Electric, Rockwell Automation, and Mitsubishi Electric, and aligns with integer and floating representations from processor families by Intel and ARM Holdings. It specifies storage allocation and variable scope for global, local, and retained variables similar to models used in embedded platforms designed by Texas Instruments and STMicroelectronics. Memory models reference practices from embedded systems research at Fraunhofer Society and academic groups at Carnegie Mellon University and University of California, Berkeley to address determinism and safety requirements found in projects by ABB and Honeywell.

Execution Models and Task Scheduling

IEC 61131-3 describes cyclic, event-driven, and interrupt-driven execution paradigms and task priorities used by runtime environments from Siemens, Rockwell Automation, and Beckhoff; these models are consistent with scheduling theory advanced at institutions like Massachusetts Institute of Technology and ETH Zurich. The standard's task mechanisms support deterministic real-time behavior required in applications by ABB and Siemens Energy and interoperate with real-time operating systems from vendors such as Wind River Systems and projects like Real-Time Linux. Execution semantics for SFC and function block instances reflect practices used in manufacturing plants operated by General Electric and Toyota.

Conformance, Implementations, and Industry Adoption

Conformance testing frameworks and certification schemes referenced by the standard are implemented by laboratories such as TÜV Rheinland and Underwriters Laboratories, and are used by automation suppliers including Siemens, Rockwell Automation, Schneider Electric, ABB, Mitsubishi Electric, and Omron. Major industrial sectors—process control, automotive, energy, and discrete manufacturing—adopt implementations influenced by consortiums and initiatives where Fieldbus Foundation, PROFIBUS, OPC Foundation, and ISA play roles. Academic research at Imperial College London and Technical University of Munich examines extensions and interoperability, while commercial toolchains from National Instruments and Siemens Digital Industries Software provide vendor-specific integrations tailored to standards-driven development.

Category:IEC standards