Engineering Questions with Answers - Multiple Choice Questions

MCQs on Interrupt and Stack of 8051 -1

1 - Question

Which of the following is an external interrupt?
a) INT0(active low)
b) INT2(active low)
c) Timer0 interrupt
d) Timer1 interrupt

View Answer
Answer: a
Explanation: INT0(active low) and INT1(active low) are two external interrupt inputs provided by 8051.

 




2 - Question

The interrupts, INT0(active low) and INT1(active low) are processed internally by flags
a) IE0 and IE1
b) IE0 and IF1
c) IF0 and IE1
d) IF0 and IF1

View Answer
Answer: a
Explanation: The interrupts, INT0(active low) and INT1(active low) are processed internally by the flags IE0 and IE1.

 




3 - Question

The flags IE0 and IE1, are automatically cleared after the control is transferred to respective vector if the interrupt is
a) level-sensitive
b) edge-sensitive
c) in serial port
d) in parallel port

View Answer

Answer: b
Explanation: If the interrupts are programmed as edge sensitive, the flags IE0 and IE1 are automatically cleared after the control is transferred to respective vector.




4 - Question

If the external interrupt sources control the flags IE0 and IE1, then the interrupt programmed is
a) level-sensitive
b) edge-sensitive
c) in serial port
d) in parallel port

View Answer

Answer: a
Explanation: If the interrupts are programmed as level sensitive, then the flags IE0 and IE1 are controlled by external interrupt sources themselves.




5 - Question

The pulses at T0 or T1 pin are counted in
a) timer mode
b) counter mode
c) idle mode
d) power down mode

View Answer

Answer: b
Explanation: In counter mode, the pulses are counted at T0 or T1 pin.




6 - Question

In timer mode, the oscillator clock is divided by a prescalar
a) (1/8)
b) (1/4)
c) (1/16)
d) (1/32)

View Answer

Answer: d
Explanation: In timer mode, the oscillator clock is divided by a prescalar (1/32) and then given to the timer.




7 - Question

The serial port interrupt is generated if
a) RI is set
b) RI and TI are set
c) Either RI or TI is set
d) RI and TI are reset

View Answer

Answer: c
Explanation: The serial port interrupt is generated if atleast one of the two bits, RI and TI is set.




8 - Question

In serial port interrupt, after the control is transferred to the interrupt service routine, the flag that is cleared is
a) RI
b) TI
c) RI and TI
d) None

View Answer

Answer: d
Explanation: In serial port interrupt, after the control is transferred to the interrupt service routine, neither of the flags are cleared.




9 - Question

The atleast number of machine cycles for which the external interrupts that are programmed level-sensitive should remain high is
a) 1
b) 2
c) 3
d) 0

View Answer

Answer: b
Explanation: The external interrupts, programmed level-sensitive should remain high for atleast 2 machine cycles.




10 - Question

If the external interrupts are programmed edge sensitive, then they should remain high for atleast
a) 0 machine cycle
b) 2 machine cycles
c) 1 machine cycle
d) 3 machine cycles

View Answer

Answer: c
Explanation: If the external interrupts are programmed edge sensitive, then they should remain high for atleast one machine cycle and low for atleast one machine cycle, for being sensed.

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