Engineering Questions with Answers - Multiple Choice Questions

MCQs on Interrupt Cycle of 8086/8088

1 - Question

If an interrupt is generated from outside the processor then it is an
a) internal interrupt
b) external interrupt
c) interrupt
d) none of the mentioned

View Answer

Answer: b
Explanation: If an external device or a signal interrupts the processor from outside then it is an external interrupt.




2 - Question

If the interrupt is generated by the execution of an interrupt instruction then it is
a) internal interrupt
b) external interrupt
c) interrupt-in-interrupt
d) none of the mentioned

View Answer

Answer: a
Explanation: The internal interrupt is generated internally by the processor circuit or by the execution of an interrupt instruction.




3 - Question

Example of an external interrupt is
a) divide by zero interrupt
b) keyboard interrupt
c) overflow interrupt
d) type2 interrupt

View Answer

Answer: b
Explanation: Since the keyboard is external to the processor, it is an external interrupt.




4 - Question

Example of an internal interrupt is
a) divide by zero interrupt
b) overflow interrupt
c) interrupt due to INT
d) all of the mentioned

View Answer

Answer: d
Explanation: Since the interrupts occur within the processor itself, they are called internal interrupts.




5 - Question

The interrupt request that is independent of IF flag is
a) NMI
b) TRAP
c) Divide by zero
d) All of the mentioned

View Answer

Answer: d
Explanation: These requests are independent of IF flag.




6 - Question

The type of the interrupt may be passed to the interrupt structure of CPU from
a) interrupt service routine
b) stack
c) interrupt controller
d) none of the mentioned

View Answer

Answer: c
Explanation: After an interrupt is acknowledged, the CPU computes the vector address from the type of the interrupt that may be passed to the internal structure of the CPU from an interrupt controller in case of external interrupts.




7 - Question

During the execution of an interrupt, the data pushed into the stack is the content of
a) IP
b) CS
c) PSW
d) All of the mentioned

View Answer

Answer: d
Explanation: The contents of IP, CS and PSW are pushed into the stack during the execution.




8 - Question

After every response to the single step interrupt the flag that is cleared is
a) IF (Interrupt Flag)
b) TF (Trap Flag)
c) OF (Overflow Flag)
d) None of the mentioned

View Answer
Answer: b
Explanation: If the trap flag is set then the processor enters the single step execution mode. After the execution, the trap flag is cleared.

 




9 - Question

At the end of ISR, the instruction should be
a) END
b) ENDS
c) IRET
d) INTR

View Answer

Answer: c
Explanation: After the execution of the ISR, the control must go to the previous program (maybe main program) which was being executed. To execute it, IRET is placed at the end of ISR.




10 - Question

When the CPU executes IRET,
a) contents of IP and CS are retrieved
b) the control transfers from ISR to main program
c) clears the trap flag
d) clears the interrupt flag

View Answer
Answer: a
Explanation: When the instruction IRET is executed, the contents of flags, IP and CS which were saved at the stack by the CALL instruction are retrieved to the respective registers.

 

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