Mitsubishi Electric FX Series - Programming; Concepts of the IEC61131-3 Standard

3 Programming
3.1 Concepts of the IEC61131-3 Standard
IEC 61131-3 is the international standard for PLC programs, defined by the International Elec
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tromechanical Commission (IEC). It defines the programming languages and structuring ele
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ments used for writing PLC programs.
This system enables structured programs to be created using a high degree of modularisation.
This provides increased efficiency, where tested programs and routines may be reused with a
reduction of the number of programming errors.
Through use of structured programming techniques, IEC1131-3 eases fault finding procedures
as individual operational program elements may be examined independently.
One important advantage of IEC61131-3 is that at assists in project management and quality
control procedures. In particular, the structured methods encompassed within IEC61131-3 aid
the Validation of processes incorporating PLC’s. In fact, in some industries it is now considered
mandatory to adopt this approach of structured programming. This is commonplace in the Phar
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maceutical and Petrochemical industries where some processes can be considered safety criti
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cal.
It is considered, in some quarters that the IEC method of programming requires excessive work
to create the final code. However, it is generally accepted that the advantages a structured
approach has to offer over “un-structured” and “open” programming techniques makes
IEC61131-3 a worthwhile advantage.
PLCopen
PLCopen has established:
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an accreditation procedure
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accredited test institutes
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development test software, shared amongst members
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a defined certification procedure
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members with certified products
This assures compliancy now, and in the future.
PLCopen Certification
Programming Concepts of the IEC61131-3 Standard
Training Manual GX IEC Developer 3 - 1
PLCopen is an independent vendor and product organisation that has been estab-
lished in order to further the use of IEC61131-3 throughout users of Industrial Con-
trol Systems. This organisation has defined 3 levels of compliancy for the design
and implementation of systems to IEC61131-3.
Mitsubishi’s GX IEC Developer is fully compli
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ant with PLCopen to “Base Level IL”(Instruc
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tion List) and “Base Level ST” (Structured
Text) and has been fully certified to these
standards.
61131-3