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IEC 1131

   What Is IEC 1131?
   Ladder Diagram
   Sequential Function Chart
   Function Block Diagram
   Structured Text
   Instruction Lists

IEC 1131 Function Block Diagram Overview
Like SFC, FBD is a graphical language that allows programming in other languages (ladder, instruction list, or structured text) to be nested within the FBD. In FBD, program elements appear as blocks which are "wired" together in a manner resembling a circuit diagram. FBD is most useful in those applications involving a high degree of information/data flow between control components, such as process control.

Function Block Diagram