The input image table file is changed to reflect the current status of input devices during the program scan phase of operation. True or False?

• A. True
• B. False
• C. It depends on the processor
• D. Not applicable to this PLC

Answer: (B)

During a PLC scan, the current state of all inputs is read at the start of the cycle and placed into the input image table. The user program then runs using those values, and only after the program finishes are outputs updated. Because the input image table is refreshed at the input scan phase, not during the program execution, the statement is false. The snapshot of inputs used by the program remains constant for that cycle, ensuring deterministic logic until the next scan begins.