Given the following set of events, show which routines the CPU is executing for
ID: 3563387 • Letter: G
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
IRQ1
25 ns
IRQ4
40 ns
IRQ6
50 ns
IRQ3
Time Action
0 ns: Start of Main Program
10ns: IRQ1
Time
Action
0 ns
Start of main program
10 ns
IRQ1
25 ns
IRQ4
40 ns
IRQ6
50 ns
IRQ3
Explanation / Answer
0 -> main
10n -> IRQ1
25n -> IRQ4,IRQ1 pending 5ns
40ns -> IRQ6,IRQ4 and IRQ1 pending 5ns
50ns -> IRQ6,IRQ3 pending 20ns,IRQ4 and IRQ1 pending 5ns
60ns ->IRQ6 completed, IRQ4 started, IRQ3 pending 20ns ,IRQ1 pending 5ns
65ns ->IRQ4 completed, IRQ3 started,IRQ1 pending 5ns
85ns ->IRQ3 completed, IRQ1 started
90ns -> IRQ1 completed, main continues.
final solution looks like:
0 - 10 -> main
10 - 25 -> IRQ1
25 - 40 -> IRQ4
40 - 60 -> IRQ6
60 - 65 -> IRQ4
65 - 85 -> IRQ3
85 - 90 -> IRQ1
90 - 100 -> main
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