data processor

A programmable logic controller (PLC) is a special data processor used as controller for machines in industrial processes. As a part of process control, a programmable logic controller is used to monitor input signals from a variety of input points which report events and conditions occurring in a controlled process. During the execution of a stored control program, they read inputs from the controlled process and, per the logic of the control program, provide outputs to the controlled process. A PLC typically consists of an input section, a logic (or processing) section, an output section, and a power supply. A PLC is typically programmed with a sequential program for controlling a machine, such as a pressing or marking machine that continuously repeats the same motions during, for example, an automated assembly process or other manufacturing process. Programmable logic controllers can be programmed using different development platforms. One common development platform is called ladder logic. Ladder logic is a programming language based on executing commands on a line-by-line permission system. Each ladder logic program comprises one or more ladder logic statements. These ladder logic statements are often termed "rungs." Each ladder logic statement defines the relationship between an output variable and one or more input variables. Programmable logic controllers are used throughout industry to control and monitor a wide range of machines and other movable components and systems. A PLC can monitor such input conditions as motor speed, temperature, pressure, volumetric flow and the like.