INTERRUPT LATENCY ANALYSIS

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Example: Interrupt Latency Analysis .ISRO takes 5 msec and occurs at most once every 15 msec .ISR1 takes 6 msec and occurs at most once every 20 msec ISR2 takes 7 msec and occurs at most once every 100 msec .ISR3 takes 9 msec and occurs at most once every 250 msec latencvkt1 max ISR, + henpc Periodr ISRr latency-945+6-20 latencys 9 +115+116-9+10-6-25 latenof=9+| 5+ |2516-9+10+12-31 latency 9515 12- 306 latency9206-915 12-36 ISR2 latency = 36 msec Question 1. Interrupt Latency Consider a system with five interrupt service routines (ISRO-4). ISRs are ordered in descending order of priority; hence, ISRO has the highest priority and ISR4 has the lowest priority. Assume that each ISR has the following characteristics: ISRO takes at most 5 msec and occurs at most once every 26 msec ISR1 takes at most 7 msec and occurs at most once every 34 msec ISR2 takes at most 8 msec and occurs at most once every 40 msec ISR3 takes at most 10 msec and occurs at most once every 100 msec ISR4 takes at most 12 msec and occurs at most once every 120 msec . Compute the worst-case latency of ISR2. Use the following recurrence equation to compute the worst-case interrupt latency: a) latencyISRn ei b) Compute the worst-case latency of ISR4 c) Suppose that ISR3's execution time is changed from 10 msec to 20 msec. In this case, what will be the worst-case latency of ISR2? Example: Interrupt Latency Analysis .ISRO takes 5 msec and occurs at most once every 15 msec .ISR1 takes 6 msec and occurs at most once every 20 msec ISR2 takes 7 msec and occurs at most once every 100 msec .ISR3 takes 9 msec and occurs at most once every 250 msec latencvkt1 max ISR, + henpc Periodr ISRr latency-945+6-20 latencys 9 +115+116-9+10-6-25 latenof=9+| 5+ |2516-9+10+12-31 latency 9515 12- 306 latency9206-915 12-36 ISR2 latency = 36 msec Question 1. Interrupt Latency Consider a system with five interrupt service routines (ISRO-4). ISRs are ordered in descending order of priority; hence, ISRO has the highest priority and ISR4 has the lowest priority. Assume that each ISR has the following characteristics: ISRO takes at most 5 msec and occurs at most once every 26 msec ISR1 takes at most 7 msec and occurs at most once every 34 msec ISR2 takes at most 8 msec and occurs at most once every 40 msec ISR3 takes at most 10 msec and occurs at most once every 100 msec ISR4 takes at most 12 msec and occurs at most once every 120 msec . Compute the worst-case latency of ISR2. Use the following recurrence equation to compute the worst-case interrupt latency: a) latencyISRn ei b) Compute the worst-case latency of ISR4 c) Suppose that ISR3's execution time is changed from 10 msec to 20 msec. In this case, what will be the worst-case latency of ISR2