Continuous function chart

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The Continuous Function Chart ( CFC ; German signal flow plan ) is a programming language for programmable logic controllers (PLC). Although it is not one of the languages ​​defined in the IEC 61131-3 standard, it is a common extension of IEC programming environments.

Its main area of ​​application is primarily in process control technology , because the complex control and regulation tasks that occur there can be mapped very well in CFC.

CFC programming

CFC is a graphic programming language in which function blocks are interconnected, instead of entering a sequence of textual commands as in classic programming languages. Circuit diagrams from hardware development can be seen as a model . This representation of a program suits developers of control software, whose technical background typically comes from electrical engineering.

CFC can be seen as an extension of the function block language , in which no strict line-by-line processing is enforced from top left to bottom right, the function blocks can be freely positioned and the programmer has more options for linking inputs and outputs. The order in which the blocks are processed is determined by numbering.

The individual function blocks themselves are often written in other PLC languages ​​such as STL or structured text and can be supplied as standard modules by the manufacturer of the automation system or written by the user himself.

Many process control systems also have visualization . For this reason, faceplates (visualization images) are often already integrated in blocks that communicate with the user of the system (operation and / or display of states), which can then be conveniently used on compatible visualization systems.

Due to the higher degree of abstraction , the translated programs with CFC are a lot more extensive than with hardware-related languages ​​such as STL. In the case of complex programs, this can lead to problems with the main memory available in the controller or the cycle time and make it necessary to use a more powerful (more expensive) controller.

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