Programming Industrial Control Systems Using IEC 1131-3
This revised edition includes all IEC proposed amendments and corrections for the planned 1999 revision of IEC 1131-3, as agreed by the IEC working group. It accurately describes the languages and concepts, and interprets the standard for practical implementation and applications.
Inspec keywords: industrial control; programmable controllers; IEC standards; signal flow graphs
Other keywords: IEC 1131-3; structured text; sequential function chart; function block diagram; instruction list; function block; ladder diagram
Subjects: Combinatorial mathematics; Combinatorial mathematics; Programmable controllers; Control technology and theory (production); Standards and calibration; Control in industrial production systems
- Book DOI: 10.1049/PBCE050E
- Chapter DOI: 10.1049/PBCE050E
- ISBN: 9780852969502
- e-ISBN: 9781849191616
- Page count: 345
- Format: PDF
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Front Matter
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1 Introduction
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This book has been written as a user guide and tutorial for the new international standard IEC 1131-3 for programmable logic controllers (PLCs). If you are considering designing or writing control programs using any of the IEC 1131-3 languages for the first time, you are advised to gain an understanding of how programs are structured and can be built up from various software elements; this is reviewed in Chapter 2, 'IEC 1131-3 concepts'. This chapter will also explain how the standard provides a selection of programming languages for developing different parts of a control program. Later chapters give specific details on using each of the IEC 1131-3 languages. The suitability of each language for solving different types of industrial control problems is described along with techniques and examples. Facilities in the IEC 1131-3 and an accompanying standard IEC 1131-5 for communicating with other PLCs and devices are discussed in Chapter 12, 'Communications'.
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2 IEC 1131-3 concepts
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This chapter discusses the IEC 1131-3 standard. It has adopted a well defined and formal model for the design of software within a PLC system. The model has been developed to cater for typical industrial applications of PLCs, including use in direct digital control systems.
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3 Common elements
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In this chapter we introduce many of the common programming elements that are used with all of the IEC languages. An understanding of how elements such as variables and data types are used is necessary before it is possible to go on to develop programs using Structured Text or any of the other languages. We will see that IEC 1131-3 provides an extensive range of common elements that can be used both with the textual languages Structured Text (ST) and Instruction List (EL), and with the graphical languages Function Block Diagram (FBD) and Ladder Diagram (LD).
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4 Structured Text
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This chapter describes structured text, a high level textual language, which is the first of the IEC languages in the set: structured text, function block diagram, ladder diagram, instruction list and sequential function chart.
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5 Function Block Diagram
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This chapter discusses the function block diagram, the first graphical language of the IEC languages in the set structured text, function block diagram, ladder diagram, instruction list and sequential function chart.
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6 Ladder Diagram
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This chapter discusses the ladder diagram. Ladder Diagram can be used to express the behaviour of functions, function blocks and programs, and also actions and transitions in Sequential Function Charts.
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7 Instruction List
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Instruction List is a low level language that can be used to express the behaviour of functions, function blocks and programs, and also actions and transitions in Sequential Function Charts.
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8 Sequential Function Chart
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This chapter reviews the IEC Sequential Function Chart (SFC) graphical language; this is the final language of the DEC languages in the set: Structured Text, Function Block Diagram, Ladder Diagram, Instruction List and Sequential Function Chart. Sequential Function Chart provides a flexible and intuitive method for graphically programming sequences of actions in a control system.
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9 Function blocks
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This chapter discusses function blocks. The use of function blocks is one of the most important concepts formalised by the IEC 1131-3 standard. Using function blocks in the design of control software has many benefits including improving software quality and productivity.
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10 Programming example
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This chapter discusses the application of IEC 1131-3 to industrial control problems. The design can be constructed to run on different PLC processing resources. The use of programs and function blocks to construct a hierarchical top-down design. The development of re-usable function blocks that can be applied to solve the same problem many times within the same system.
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11 Programming station facilities
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In this chapter the features of a programming station suitable for developing software for IEC based PLCs are reviewed. As the standard has only recently been published, there are few PLC products on the market today that can offer all the features discussed in this chapter.
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12 Communications
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This chapter reviews part 5 of the IEC 1131 standard, which focuses solely on PLC communications. In this chapter, it reviews the main scope of the IEC 1131-5 standard, the communications model, the PLC functional model, accessing PLC status information, communications function blocks, mapping of communications function blocks on to MMS.
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Appendix 1: IEC 1131-3 keywords
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This appendix contains a list of keywords used in the IEC languages. To avoid the possibility of having ambiguous language identifiers, the names of the following keywords should be regarded as reserved and not used as identifiers.
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Appendix 2: IEC 1131-3 amendments
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IEC is working on new editions of IEC 1131-3 indicates that it is an emerging standard that will continue to be refined and extended as users start to apply the IEC 1131-3 concepts and languages to the development of mainstream control system software.
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Appendix 3: IEC 1131-3 frequently asked questions (FAQ)
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The following list is a compilation of frequently asked questions about IEC 1131-3. The reader should be aware that it has been the author's best intention that the answers to these questions are correct. However, in due course, it is possible that changes in new editions of the standard may modify or possibly invalidate some of the answers.
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Appendix 4: IEC 1131-3 future developments
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During the next few years the main focus of IEC 1131-3 standardisation work is clearly going to concern language concepts and extensions for building distributed applications. Recent developments in the use of distributable software components and concepts such as re-usable software as function blocks are likely to have a major impact in this area. The IEC and the international standardisation bodies have done a great deal of work to create standards in this area. In the long term, the unification of software languages and architectures for distributed industrial control applications will bring major economic advantages to end-users and system builders alike.
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Back Matter
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