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Simple function block diagram. The function block diagram (FBD) is a graphical language for programmable logic controller design, [1] that can describe the function between input variables and output variables. A function is described as a set of elementary blocks. Input and output variables are connected to blocks by connection lines.
As programming terminals evolved, because ladder logic was a familiar format used for electro-mechanical control panels, it became more commonly used. Newer formats, such as state logic, [18] function block diagrams, and structured text exist. Ladder logic remains popular because PLCs solve the logic in a predictable and repeating sequence, and ...
ST (structured text) is similar to programming in Pascal or C; LD (ladder diagram) enables programmers to virtually combine relay contacts and coils; FBD (function block diagram) enables users to rapidly program both Boolean and analog expressions; SFC (sequential function chart) is convenient for programming sequential processes and flows
Example of SCADA used in office environment to remotely monitor a process. Both large and small systems can be built using the SCADA concept. These systems can range from just tens to thousands of control loops, depending on the application. Example processes include industrial, infrastructure, and facility-based processes, as described below:
Part 3 of IEC 61131 deals with basic software architecture and programming languages of the control program within PLC. It defines three graphical and two textual programming language standards: Ladder diagram (LD), graphical; Function block diagram (FBD), graphical; Structured text (ST), textual
Sequential function chart (SFC) is a visual programming language used for programmable logic controllers (PLCs). It is one of the five languages defined by IEC 61131-3 standard. The SFC standard is defined as Preparation of function charts for control systems , and was based on GRAFCET [ fr ] (itself based on binary Petri nets [ 1 ] [ 2 ] ).
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Function blocks (FB) - contain frequently occurring and particularly complex program parts; Data blocks (DB) - for storing data required for processing the control program. Some S5 PLCs also have block types FX (Extended Function Blocks), and DX(Extended Data Blocks); these are not distinct block types, but rather are another set of available ...