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If the PendSV exception priority is set lower than SysTick, what is the expected behavior when both exceptions are pending?

medium📝 Analysis Q5 of 15
ARM Architecture - Exception and Interrupt Model
If the PendSV exception priority is set lower than SysTick, what is the expected behavior when both exceptions are pending?
APendSV exception is handled first, then SysTick
BNeither exception is handled until reset
CBoth exceptions are handled simultaneously
DSysTick exception is handled first, then PendSV
Step-by-Step Solution
Solution:

  1. Step 1: Understand priority rules

    Lower numerical priority value means higher priority in ARM Cortex-M.

  2. Step 2: Apply to given case

    SysTick has higher priority, so it is handled before PendSV.

  3. Final Answer:

    SysTick exception is handled first, then PendSV -> Option D

  4. Quick Check:

    Higher priority exception handled first = SysTick [OK]
Quick Trick: Lower priority number means higher priority [OK]
Common Mistakes:
  • Assuming PendSV always runs first
  • Thinking exceptions run simultaneously
  • Believing exceptions wait indefinitely

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