How do I/O modules communicate with the PLC processor?

How do I/O modules communicate with the PLC processor?

• A. The input module transmits data to the processor on a regular basis so that the processor can collect the information via scan.
• B. The input module stores data locally and does not communicate with the processor.
• C. The input module only sends data when manually triggered by a technician.
• D. The input module uses wireless to report data to a separate controller.

Answer: (A)

I/O modules communicate with the PLC processor through a regular scan cycle. At the start of each cycle, the input modules sample their physical signals (sensors, switches) and place those values into the processor’s input image. The processor then executes the program using those current input values. After the logic runs, the processor writes the results to the output image, and the output modules drive the actual physical outputs. This cyclic, synchronized data exchange keeps the system deterministic and ready to respond to changes on every scan. That’s why the other options don’t fit: inputs aren’t stored locally without communicating with the processor, they aren’t sent only when manually triggered, and standard I/O typically isn’t wireless reporting to a separate controller within the core PLC operation.

I/O modules communicate with the PLC processor through a regular scan cycle. At the start of each cycle, the input modules sample their physical signals (sensors, switches) and place those values into the processor’s input image. The processor then executes the program using those current input values. After the logic runs, the processor writes the results to the output image, and the output modules drive the actual physical outputs. This cyclic, synchronized data exchange keeps the system deterministic and ready to respond to changes on every scan.

That’s why the other options don’t fit: inputs aren’t stored locally without communicating with the processor, they aren’t sent only when manually triggered, and standard I/O typically isn’t wireless reporting to a separate controller within the core PLC operation.