Given the following set of events, show which routines the CPU is executing for

Question

Given the following set of events, show which routines the CPU is executing for times 0 to 100 ns. Each handler routine (with its interrupt request) takes 20 ns to complete. The priority of the interrupts ranges from IRQ6 as the highest priority interrupt to IRQ0 as the lowest priority interrupt.

Time

Action

0 ns

Start of main program

10 ns

IRQ5

25 ns

IRQ3

40 ns

IRQ4

50 ns

IRQ2

            Time                Action

0 ns:                Start of Main Program

10 ns: IRQ5

Time

Action

0 ns

Start of main program

10 ns

IRQ5

25 ns

IRQ3

40 ns

IRQ4

50 ns

IRQ2

Explanation / Answer

As the interrupt will complete one instruction in 20 ns that means after 20nsec, a next interrupt will be handeled no matter the previous one is completed or not,hence
0-10 ns-> IRQ5
10-30ns -> IRQ4
30-65ns->IRQ3
And in parallel to IRQ3, from 50ns, the IRQ2 will start
50-100 ns-> IRQ2

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