Logic functions AND, OR, EXCLUSIVE OR, NAND, and NOR, as well as latching, are represented in this Functional Block diagram for Three phase load using standard programming techniques such as ladder and function block programming. Most PLCs are programmed using the ladder programming LAD method. A single rung represents an operation in the control process on the ladder, which begins with one or more inputs and ends with one or more outputs. By starting at the left and working our way to the right, the END rung marks the end of the program's rung scan. After that, the loop begins again in an infinite loop generated by the program.
