Instruction list (IL) is one of the 5 languages supported by the initial versions of
IEC 61131-3
IEC 61131-3 is the third part (of 10) of the international standard IEC 61131 for programmable logic controllers. It was first published in December 1993 by the IEC; the current (fourth) edition was published in May 2025.
Part 3 of ''IEC 61131' ...
standard, and subsequently deprecated in the third edition.
It is designed for
programmable logic controller
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that ...
s (PLCs). It is a
low level language and resembles
assembly. All of the languages share
IEC61131 Common Elements. The variables and function call are defined by the common elements so different languages can be used in the same program.
Program control (
control flow
In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an '' ...
) is achieved by ''
jump'' instructions and function calls (
subroutines
In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times.
Callable units provide a p ...
with optional parameters).
The file format has now been standardized to
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...
by
PLCopen.
Example
Variations from IEC 61131
Many vendors whilst incorporating the full
IEC 61131-3
IEC 61131-3 is the third part (of 10) of the international standard IEC 61131 for programmable logic controllers. It was first published in December 1993 by the IEC; the current (fourth) edition was published in May 2025.
Part 3 of ''IEC 61131' ...
requirements have additional vendor specific calls/function blocks to suit their hardware such as reading or writing to I/O.
Siemens PLC instruction list language is known as "Statement List" or "STL" in English, and "Anweisungs-Liste" or "AWL" in German, Italian and Spanish. The user of a Simatic development package may choose between German and International
mnemonics
A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember.
It makes use of e ...
to represent instructions. For example, "A" for "AND" or "U" for "UND", "I" for "Input" or "E" for "Eingang".
See also
*
1-bit architecture
References
External links
*
IEC 61131-3
Programmable logic controllers
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