Programming methods of IEC 61131-3

The IEC61131-3 standard defines 5 programming methods for PLCs:

  • Ladder diagrem (LD)
  • Functional block diagram (FBD)
  • Structured text (ST)
  • Instruction list (IL)
  • Sequential function chart (SFC)

Function Block diagram is a programming method, which allows easy graphical programming via pre-programmed function blocks. Those blocks are to be interconnected with other blocks or input / output variables. Each function block describes the relation between the input and output variable. It is possible to either import FB or make your own.