Archive for the ‘IEC 61131-3 (english)’ Category

IEC 61131-3: The ‘Decorator’ Pattern

February 16, 2019 1 comment

With the help of the decorator pattern, new function blocks can be developed on the basis of existing function blocks without overstraining the principle of inheritance. In the following post, I will introduce the use of this pattern using a simple example.

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IEC 61131-3: The ‘State’ Pattern

November 17, 2018 5 comments

State machines are used regularly, especially in automation technology. The state pattern provides an object-oriented approach that offers important advantages especially for larger state machines.

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IEC 61131-3: The generic data type T_Arg

In the article The wonders of ANY, Jakob Sagatowski shows how the data type ANY can be effectively used. In the example described, a function compares two variables to determine whether the data type, data length and content are exactly the same. Instead of implementing a separate function for each data type, the same requirements can be implemented much more elegantly with only one function using data type ANY.

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IEC 61131-3: The ‘Observer’ Pattern

The Observer Pattern is suitable for applications that require one or more function blocks to be notified when the state of a particular function block changes. The assignment of the communication participants can be changed at runtime of the program.

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IEC 61131-3: Unit-Tests

January 24, 2018 4 comments

Unit tests are an essential tool for every programmer to ensure functioning of his software. Software bugs cost time and money, so you need an automated solution to find these bugs and preferably before the software is used. Unit tests should be used wherever software is professionally developed. This article is intended to provide a quick introduction and allow an understanding of the benefits of unit tests.

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IEC 61131-3: Extend UNION via inheritance

September 24, 2017 1 comment

In the post IEC 61131-3: Additional language extensions, I briefly described the UNION. A reader comment has pointed out to me the possibility, that a UNION can also be expanded by EXTENDS. Since this simplifies the handling of a UNION and the norm does not indicate that, I would like to introduce this possibility in a (very) short post. Read more…

IEC 61131-3: Parameter transfer via parameter list

September 10, 2017 2 comments

Parameter lists are an interesting alternative for transferring parameters to PLC libraries. Strictly speaking, these are global constants (VAR_GLOBAL CONSTANT) whose initialization values can be edited in the Library Manager.

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