Software construction guidelines released

The PLCopen Coding Guidelines version 1.0 has been released and contains 63 rules for software programming and are designed to train users and provide a basis for universities to help them teach IEC 61131-3 programming more efficiently.


The PLCopen Coding Guidelines version 1.0 has been released and is available for download. Version 1.0 contains 63 rules for software programming, which is spread over different sections such as naming rules, comment rules, coding practice, languages, and vendor specific IEC 61131-3 extensions. These rules are designed to train users and provide a basis for universities to help them teach IEC 61131-3 programming more efficiently.

Software today often absorbs half of the initial project costs and between 40 and 80% deals with maintenance over the life cycle costs of the software. In order to deal with the complexity of larger programs, modern software development processes supporting a structured approach and creating re-usable code are needed. Also, the efficiency in coding needs to be increased via re-use of pre-defined functionalities and to help to better understand the program over the life cycle.

Since the release of the first documents, further work was done on the following topics:

  • Creating PLCopen compliant function block libraries
  • Structuring and decomposition via sequential function charts (SFCs).

Both areas are close to publishing their first results. The libraries are giving guidance and examples to create own libraries. For this, templates are provided for the two basic function blocks operation differences: edge-triggered or level-triggered. This basis is extended with time-out functionality and a timer to spread an operation over multiple operating cycles. The included examples show the basic code as provided by the 3rd edition of the IEC 61131-3 standard.

Additional working groups active under the software construction guidelines will focus on the following topics:

  • Guidance for documentation in software programs
  • Software quality issues and software consistency
  • Software development process
  • Object orientation in the 3rd edition.


- Edited from a PLCopen press release by CFE Media. See more Control Engineering PLC and PAC stories.

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Learn more about PLC Coding Guidelines version 1.0 here.

Tisha , MI, United States, 10/20/16 03:17 PM:

I am extremely excited for the guidelines!

Often I run into programs that are so fundamentally poorly written. This document provides a means for programmers to educate themselves. It gives a concrete way of holding each other, or even just yourself, accountable. And what might be most beneficial for me, it gives a concrete reference to what good programming practice looks like to which others can point to.

I cannot thank the group enough for creating this document.
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