CyberCertPrepOT Security FundamentalsOT Fundamentals: ICS/SCADA BasicsHARDFree question
A PLC with a 20 ms scan time sees an input pulse lasting 5 ms that rises and falls between two input reads. What happens?
- A.The controller faults with a watchdog error at once
- B.The scan time shortens to match the pulse width
- C.The logic can miss the pulse entirely
- D.The pulse is stored by the output image table
Why C is correct
Inputs are only sampled once per scan, so a pulse shorter than the scan interval can fall between samples. Fast events need interrupt inputs or high-speed counters. The output image table does not latch inputs and scan time is not adaptive.
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