Based on the industrial control programming language standards set by the电工委员会 (IEC 1131-3), PLCs have five standard programming languages: Ladder Diagram (LD), Instruction List (IL), Function Block Diagram (FBD), Sequential Function Chart (SFC), and Structured Text (ST). These five programming languages are very simple and easy to learn.

Ladder Diagram Language (LD)

Ladder logic is a commonly used programming language in PLC design. It is a programming language similar to relay circuitry. As electrical designers are generally familiar with relay control, the ladder logic programming language has gained widespread popularity and application.

The features of trapezoidal diagram programming language include: corresponding to electrical operation diagrams with intuitiveness and correspondence; consistent with existing relay control, making it easy for electrical designers to master.

Ladder logic programming differs from the original relay control in that the energy flow in ladder diagrams is not actual current, and the relays within are not physically existing relays. When applying ladder logic, it is necessary to differentiate from the original relay control concept.