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This document introduces the history of Programmable Logic Controllers (PLCs) as well as their components and modes of operation.
It explains what the IEC-61131-3 PLC programming standard consists of. IN 1993: The International Electrotechnical Commission (IEC) published the IEC 61131 standard for PLC hardware and software requirements.
IEC-61131-3 offers 5 programming languages.
Textual languages:
- Instruction List (IL)
- Structured Text (ST)
Graphic languages:
- Function Block Diagram (FBD)
- Ladder Diagram (LD)
- Sequential Functional Chart (SFC)
It also explains variables, data types, and common elements used in PLC programs.