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If an ARM processor executes WFI but no interrupt occurs, what is the processor's state?

medium📝 Analysis Q5 of 15
ARM Architecture - Power Modes
If an ARM processor executes WFI but no interrupt occurs, what is the processor's state?
AIt remains in low-power sleep mode indefinitely
BIt automatically wakes after a fixed time
CIt shuts down completely
DIt resets and restarts execution
Step-by-Step Solution
Solution:

  1. Step 1: Understand WFI wait condition

    The processor stays in sleep mode until an interrupt or event wakes it.

  2. Step 2: Check if automatic wake-up exists

    WFI does not include automatic wake-up or reset features.

  3. Final Answer:

    It remains in low-power sleep mode indefinitely -> Option A

  4. Quick Check:

    WFI waits indefinitely for interrupt [OK]
Quick Trick: No interrupt means CPU stays asleep with WFI [OK]
Common Mistakes:
  • Thinking WFI wakes automatically
  • Assuming processor shuts down
  • Believing WFI causes reset

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