Consider the following two statements about interrupt handling mechanisms in a…
2026
Consider the following two statements about interrupt handling mechanisms in a CPU.
S1: In non-vectored interrupt mechanism, it usually takes more time to start the Interrupt Service Routine (ISR) when compared to that in a vectored interrupt mechanism.
S2: In daisy-chain interrupt mechanism, the CPU polls all the input devices individually to determine the source of the interrupt.
Which one of the following options is correct?
- A.
Both S1 and S2 are true
- B.
Both S1 and S2 are false
- C.
S1 is true and S2 is false
- D.
S1 is false and S2 is true
Attempted by 64 students.
Show answer & explanation
Correct answer: C
Statement S1
In non-vectored interrupt mechanism, it usually takes more time to start the Interrupt Service Routine (ISR) when compared to that in a vectored interrupt mechanism.
This statement is True.
In a vectored interrupt, the interrupting device directly provides the ISR address (or vector number), so the CPU can immediately jump to the corresponding ISR.
In a non-vectored interrupt, the CPU must first identify which device generated the interrupt, usually through additional checking or polling. This extra step increases the interrupt response time.
Therefore, non-vectored interrupts generally take more time to begin ISR execution.
Statement S2
In daisy-chain interrupt mechanism, the CPU polls all the input devices individually to determine the source of the interrupt.
This statement is False.
In a daisy-chain interrupt mechanism, devices are connected serially according to priority. The interrupt acknowledge signal passes through the chain, and the highest-priority requesting device captures it and responds.
The CPU does not poll every device individually. Priority resolution is handled by the hardware chain itself.
Correct Option
Option C: S1 is true and S2 is false