Interrupt and Stack of 8051 Questions

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1.

Which of the following is an external interrupt?

A

INT0(active low)

B

INT2(active low)

C

Timer0 interrupt

D

Timer1 interrupt

Correct Answer: A

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2.

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

Correct Answer: A

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3.

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

Correct Answer: B

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4.

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

Correct Answer: A

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5.

The pulses at T0 or T1 pin are counted in

A

timer mode

B

counter mode

C

idle mode

D

power down mode

Correct Answer: B

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6.

In timer mode, the oscillator clock is divided by a prescalar

A

(1/8)

B

(1/4)

C

(1/16)

D

(1/32)

Correct Answer: D

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7.

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

Correct Answer: C

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8.

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

Correct Answer: D

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9.

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

Correct Answer: B

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10.

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

Correct Answer: C

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