Fundamentals And Applications Of Programmable Logic Controllers Research Paper

Fundamentals And Applications Of Programmable Logic Controllers - Research Paper Example The vast number of advantages offered by Programmable logic controllers in industrial automation has ensured their predominance over the last decades and some years to come. Programmable logic controllers are cost effective for the control of complex systems, flexible and can be easily reapplied to control other systems, simplified programming and reduced downtime given their troubleshooting aid, sophisticated control owing to their computational abilities and long-term operation capability without failure given their reliable components. (Evans, 2006) The central processing unit (CPU) is involved with the performance of logic and arithmetic functions of a PLC. It utilizes the program stored in memory to process the accepted input signal from the input modules into the desired output. It sends the desired output signal to the output modules which converts it into an appropriate actuator signal. In general, the CPU performs the functions of updating the input and output, logic and arithmetic functions and memory communication. The CPU is further divided into three major subsystems; Control Unit (CU), Arithmetic and Logic Unit (ALU) and the Registers. Instructions are fetched from a specified location and loaded into the registers then decoded by the Control Unit. The arithmetic and logic operations such as the subtraction, addition and basic logic operations such as OR/AND are done by the ALU. Control Unit directs the results into a special memory location for storage. Arithmetic and Logic Unit (ALU) is a logic gate collection with outputs, inputs and control bits for determining operation type.