Comprehensive Overview: Major Parts of Sequential Function Chart (SFC)

This report provides a detailed overview of the major components of a Sequential Function Chart (SFC), which is a graphical programming language used in programmable logic controllers (PLCs). The report begins by defining a function chart and its role in executing specific functions or events, referencing the IEC 61131-3 standards. It then delves into the three key stages: the sequential operation step (represented by a double-line rectangle), the transition condition (represented by horizontal lines and bars), and the action stage. The report explains the flow of operations, the significance of transition conditions in activating or deactivating steps, and the final stage's role in producing the desired output. The report includes examples and emphasizes that physical inputs are not considered execution or transition actions. References to Simon & Kowalewski (2016) and Mohamed & Karim (2016) are included for further context.

Major Parts of Sequential Function Chart
Major Parts of Sequential Function Chart
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Major Parts of Sequential Function Chart
Major parts of the sequential function chart
A function chart refers to a series of graphical programming language used in
programmable logic control (PLC) to initiate and execute a specific function or event. The
function chart is one of the ICE 61131-3 PLC programming language with its basics of operation
detailed in the IEC 848 standards (Simon & Kowalewski, 2016). The function chart involves the
execution of activities in sequential order, and the task execution occurs in three major stages or
parts, that are the sequential operation step, the transition stage, and the final step of actualization
or action stage.
The first part of the function chart is the initiation step. This stage is graphically
represented by the use of a double- line rectangle. In logic programming, the rectangle indicates
the first action in ladder logic with operation descriptions indicated on the left side of the
rectangle box. The flow of operations in function chart, not unless indicated or stated otherwise,
is assumed to be flowing from top to down (Mohamed & Karim, 2016). Actions associated with
each step can either be active or inactive depending on the logic instruction; therefore, this stage
that describes the related action will only activate the second stage if the set logic instructions
activate it
The second part is the transition condition. In a programming language, this is often
represented by horizontal lines and bars between steps, and this stage controls the operations of
steps in that if the instructions in the active phase is correct then the stage is deactivated and the
preceding step is activated, and the sequential operations flows up to the end of the flow
diagram. Step execution stops at the end of the flow chart, where it is signalized by the presence

Major Parts of Sequential Function Chart
of a blank circle indicating the end of the program or any other instruction to repeat the cycle
(Simon & Kowalewski, 2016).
The final stage of function chart is the action of each step in a chronological order to
provide a sound output as defined by the keyed inputs. This gives the outcome of each step
executed in the ladder logic (Mohamed & Karim, 2016). For example, the blinking of traffic
lights, as instructed in the PLC, is a typical example of the outcome of the instructions given to
the machine.
Designing a function chart involve use of coded language that produces the desired
action, therefore, physical inputs are not considered as execution actions or transition actions, so
when designing a functional chart physical inputs and outputs are never regarded as steps of
operation

Major Parts of Sequential Function Chart
Reference
Simon, H., & Kowalewski, S. (2016, September). Static analysis of Sequential Function
Charts using abstract interpretation. In 2016 IEEE 21st International Conference on Emerging
Technologies and Factory Automation (ETFA) (pp. 1-4). IEEE.
Mohamed, T. B. H., & Karim, N. S. B. H. A. (2016). An application of sequential
function chart (sfc) in automation system. JSET, 3(2), 35-39.