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IEC 61131-3 PLC programming languages (LD, FBD, SFC, ST, and IF)
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
There are five programming languages that are defined by Part 3 of the International Electrotechnical Commission standard IEC 61131, consisting of three graphical languages being Ladder Diagram, Function Block Diagram, and Sequential Function Chart, and two textual languages consisting of Structured Text and Instruction list. Many PLC manufacturers tend to use the IEC standard as a guide, with some nuances of syntax. The various programming languages have different strengths for different tasks, and many higher-end programming languages provide the ability to mix the languages within a single program. In some instances, program code can be obtained from equipment manufacturers to streamline the integration process between programs and devices. The PLC programs have the ability to use subroutines and jump statements to reduce the amount of code and to speed operation. Often, the choice of program language is a mix of personal preference, ease of producing desired certain functions, and speed requirements.
Sequential Function Charts
Published in Murat Uzam, PIC16F1847 Microcontroller-Based Programmable Logic Controller, 2020
The IEC 61131-3 standard defines two graphical languages, namely ladder diagrams (LD) and function block diagram (FBD), and two text-based languages, namely instruction list (IL) and structured text (ST), for use in PLC programming. The graphical languages use symbols to program control instructions, while the text-based languages use character strings to program instructions. The IEC 61131-3 standard includes an additional programming framework called sequential function charts (SFC). Sometimes SFC is categorized as an IEC 61131-3 language, but it is actually an organizational structure that coordinates the standard’s four true programming languages, i.e., LD, FBD, IL, and ST. The SFC structure is much like a flowchart-type of programming framework, utilizing different languages for different control tasks and also routing control program actions [R5.1].
Programmable Logic Controller (PLC)
Published in Chanchal Dey, Sunit Kumar Sen, Industrial Automation Technologies, 2020
At the early stage of PLC programming there was no standard. Manufacturers used to develop their own programming techniques and hence users faced difficulties if they intended to change their existing PLC programs. To overcome this limitation, an international standard was adopted in December 1993 by International Electrotechnical Commission (IEC). At present, this standard is defined as IEC 61131-3, which deals with basic software architecture and programming languages of the control program for PLC. It defines two graphical and two textual programming language standards:Ladder diagram – graphicalFunction block diagram – graphicalStructured text – textualInstruction list – textual (deprecated in 3rd edition of the standard)Sequential function chart – graphical and textual. It has elements to organize programs for sequential and parallel control processing.
A Bio-Inspired, Self-Healing, Resilient Architecture for Digital Instrumentation and Control Systems and Embedded Devices
Published in Nuclear Technology, 2018
Shawkat S. Khairullah, Carl R. Elks
International Electrotechnical Commission (IEC) 1131 is a widely used de facto standard for programmable logic controllers (PLCs) and I&C systems. The purpose of IEC 1131 is to support a standard programing model for PLCs. Among the programming models endorsed by IEC 1131 is the Function Block Diagram language; these standards define the operational semantics for each FB in the program.19,20 In BioSymPLe, we decided early on to adopt the concept of the function block programming model to facilitate portability to the PLC and digital automation community. While our function blocks are not semantically equivalent to IEC 1131, our AFB model is closely related to the semantics of IEC 1131 and IEC 61499 (e.g., distributed function block programming standard). The proposed AFB shown in Fig. 5 is built based on our previous work21,22 on the concept of PLCs, and it is divided into three divisions: control flow, 1131-based data flow, and LUT-based data flow.