The CPU in a PLC serves a very important function being the center processing unit or the brain in relation to the system. They implement the flowchart control, respond to inputs from signals obtained from the sensors and produce signals to manage the other components like the actuators, motors among other machinery. This allows the PLC to control industrial processes effectively; it also reduces the time of controlling processes.
Part of the CPU is to read through the user-defined program linearly and evaluate the instructions to determine how the system has to work. In doing so it permanently checks the input signals and compares them with the program given and comes to output decisions in accordance therewith. This scanning cycle remains complete in cycles so as to keep a real time control on the process.
Besides logical computing, the CPU controls data transfers within the PLC system via data links with other units including I/O modules and memory. It also plays the role of gate way through which it interfaces with other systems or devices within the environment in which the PLC exists.
The CPU is vital to functioning of the PLC as it allows it to process information from the environment with immediate feedback on processes changes and control and correct functioning of automated systems in Industrial settings.