Posts Tagged ‘Inheritance’

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 4 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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IEC 61131-3: Additional language extensions

June 17, 2017 8 comments

The focus of my post has been the object-oriented extensions so far. But there are several general, usually not so far-reaching innovations within TwinCAT 3. Below, they are briefly described.

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IEC 61131-3: Methods, Properties and Inheritance

April 23, 2017 7 comments

Object-oriented programming (OOP) is a proven way of keeping the complexity of software systems in check. Until recently the preserve of languages such as C++, Java and C#, IEC 61131-3 introduces the concept to PLC programming.

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IEC 61131-3: The ‘Command’ Pattern

December 7, 2016 5 comments

A command can be run on a function block by calling a method. Function block A calls a method of function block B. So far, so good, but how can such “commands” be exchanged flexibly between several function blocks. The command pattern provides an interesting approach.

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IEC 61131-3: Namespaces

November 22, 2016 4 comments

The third edition of IEC 61131-3 introduces the concept of namespaces. Namespaces group elements such as variables, function blocks, data types and libraries into coherent units. This means that elements are no longer identified solely using their names, but additionally using the associated namespace.

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IEC 61131-3: Arrays with variable length

September 27, 2016 4 comments

While declaring arrays, one had always to define a constant value up to now. Since the 3rd edition of the IEC 61131-3, arrays can be declared with a variable length. Thus, you can create functions much more generically than previously.

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