Which component of a PLC is primarily responsible for executing control logic?

Which component of a PLC is primarily responsible for executing control logic?

• A. Processor
• B. Input assembly
• C. Output assembly
• D. Power supply

Answer: (A)

Executing control logic is handled by the processor, the brain of the PLC. It contains the CPU and runs the control program stored in memory. During each PLC scan, it reads input states, executes the ladder or other language instructions, performs the necessary operations (logical, arithmetic, timers, counters), and then updates the outputs through the output module. The input assembly simply collects signals from field devices and presents them to the processor; it does not run the logic. The output assembly receives commands from the processor to actuate devices; it doesn’t decide what to do. The power supply just provides power to all modules and does not process logic. So the processor is the primary component responsible for executing control logic.

Executing control logic is handled by the processor, the brain of the PLC. It contains the CPU and runs the control program stored in memory. During each PLC scan, it reads input states, executes the ladder or other language instructions, performs the necessary operations (logical, arithmetic, timers, counters), and then updates the outputs through the output module. The input assembly simply collects signals from field devices and presents them to the processor; it does not run the logic. The output assembly receives commands from the processor to actuate devices; it doesn’t decide what to do. The power supply just provides power to all modules and does not process logic. So the processor is the primary component responsible for executing control logic.