Frequently Asked microcontroller Interview questions

1. What are the flags in 8086? - In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
2. What are the various interrupts in 8086? - Maskable interrupts, Non-Maskable interrupts.
3. What is meant by Maskable interrupts? - An interrupt that can be turned off by the programmer is known as Maskable interrupt.

4. What is Non-Maskable interrupts? - An interrupt which can be never be turned off (ie.disabled) is known as Non-Maskable interrupt.
5. Which interrupts are generally used for critical events? - Non-Maskable interrupts are used in critical events. Such as Power failure, Emergency, Shut off etc.,
6. Give examples for Maskable interrupts? - RST 7.5, RST6.5, RST5.5 are Maskable interrupts
7. Give example for Non-Maskable interrupts? - Trap is known as Non-Maskable interrupts, which is used in emergency condition.
8. What is the Maximum clock frequency in 8086? - 5 Mhz is the Maximum clock frequency in 8086.
9. What are the various segment registers in 8086? - Code, Data, Stack, Extra Segment registers in 8086.
10. Which Stack is used in 8086? - LIFO (First In last Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
11. What are the address lines for the software interrupts? -
RST 0 0000 H
RST1 0008 H
RST2 0010 H
RST3 0018 H
RST4 0020 H
RST5 0028 H
RST6 0030 H
RST7 0038 H
12. What is SIM and RIM instructions? - SIM is Set Interrupt Mask. Used to mask the hardware interrupts. RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.
13. Which is the tool used to connect the user and the computer? - Interpreter is the tool used to connect the user and the tool.
14. What is the position of the Stack Pointer after the PUSH instruction? - The address line is 02 less than the earlier value.
15. What is the position of the Stack Pointer after the POP instruction? - The address line is 02 greater than the earlier value.
16. Logic calculations are done in which type of registers? - Accumulator is the register in which Arithmetic and Logic calculations are done.
17. What are the different functional units in 8086? - Bus Interface Unit and Execution unit, are the two different functional units in 8086.
18. Give examples for Micro controller? - Z80, Intel MSC51 &96, Motorola are the best examples of Microcontroller.
19. What is meant by cross-compiler? - A program runs on one machine and executes on another is called as cross-compiler.
20. What are the address lines for the hardware interrupts? -
RST 7.5 003C H
RST 6.5 0034 H
RST 5.5 002C H
TRAP 0024 H
21. Which Segment is used to store interrupt and subroutine return address registers? - Stack Segment in segment register is used to store interrupt and subroutine return address registers.
22. Which Flags can be set or reset by the programmer and also used to control the operation of the processor? - Trace Flag, Interrupt Flag, Direction Flag.
23. What does EU do? - Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.
24. Which microprocessor accepts the program written for 8086 without any changes? - 8088 is that processor.
25. What is the difference between 8086 and 8088? - The BIU in 8088 is 8-bit data bus & 16- bit in 8086.Instruction queue is 4 byte long in 8088and 6 byte in 8086.

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Written Interview Apptitude Questions

1.Three types of tea the a,b,c costs Rs. 95/kg,100/kg and70/kg respectively.

How many kgs of each should be blended to produce 100 kg of mixture worth Rs.90/kg,

given that the quntities of band c are equal

a)70,15,15

b)50,25,25

c)60,20,20

d)40,30,30


Ans: (b)


2.What is the maximum number of half-pint bottles of cream that can be filled with a 4-gallon can of cream (2 pt. =1 qt. and 4 qt. =1 gal)

A.16

B.24

C.30

D.64


Ans: D


3.There are two circles, one circle is inscribed and another circle is circumscribed over a square. What is the ratio of area of inner to outer

circle?

Ans: 1 : 2


4.In the following figure: A B C

D

E F G

H

I

Each of the digits 1, 2, 3, 4, 5, 6, 7, 8, and 9 is:

a)Represented by a different letter in the figure above.

b) Positioned in the figure above so that each of A + B + C,C + D +E,E + F + G, and G + H + I is equal to 13.

Which digit does E represent?


Ans: E is 4


5.There are 12 boys and 15 girls, How many different dancing groups can be formed with 2 boys and 3 girls.

48Which of the following fractions is less than 1/3

(a) 22/62

(b) 15/46

(c) 2/3

(d) 1


Ans: (b)


6.One of Mr. Horton,his wife,their son,and Mr. Horton's mother is a doctor and another is a lawyer.

a)If the doctor is younger than the lawyer, then the doctor and the lawyer are not blood relatives.

b)If the doctor is a woman, then the doctor and the lawyer are blood relatives.

c)If the lawyer is a man, then the doctor is a man.

Whose occupation you know?


Ans: Mr. Horton:he is the doctor.


7.A person wants to buy 3 paise and 5 paise stamps costing exactly one rupee. If he buys which of the following number of stamps he won't able to

buy 3 paise stamps.

Ans: 9


8.Mr. and Mrs. Aye and Mr. and Mrs. Bee competed in a chess tournament.Of the three games played:

a)In only the first game werethe two players married to each other.

b)The men won two games and the women won one game.

c)The Ayes won more games than the Bees.

d)Anyone who lost game did not play the subsequent game.

Who did not lose a game?


Ans:Mrs.Bee did not lose a game.


9.Two cars are 15 kms apart. One is turning at a speed of 50kmph and the other at 40kmph . How much time will it take for the two cars to meet?


Ans: 3/2 hours


10.Three piles of chips--pile I consists one chip, pile II consists of chips, and pile III consists of three chips--are to be used in game played by

Anita and Brinda.The game requires:

a)That each player in turn take only one chip or all chips from just one pile.

b)That the player who has to take the last chip loses.

c)That Anita now have her turn.

From which pile should Anita draw in order to win?


Ans:Pile II


11. 9.In a class composed of x girls and y boys what part of the class is composed of girls

A.y/(x + y)

B.x/xy

C.x/(x + y)

D.y/xy

Ans:C


12.One of the following is my secret word:AIM DUE MOD OAT TIE.With the list in front of you, if I were to tell you any one of my secret word,

then you would be able to tell me the number of vowels in my secret word.Which is my secret word?

Ans:TIE


13.If the operation,^ is defined by the equation x ^ y = 2x + y,what is the value of a in 2 ^ a = a ^ 3

A.0

B.1

C.-1

D.4

Ans:B


14.A coffee shop blends 2 kinds of coffee,putting in 2 parts of a 33p. a gm. grade to 1 part of a 24p. a gm.If the mixture is changed to 1 part

of the 33p. a gm. to 2 parts of the less expensive grade,how much will the shop save in blending 100 gms.

A.Rs.90

B.Rs.1.00

C.Rs.3.00

D.Rs.8.00


Ans:C


15.There are 200 questions on a 3 hr examination.Among these questions are 50 mathematics problems.It is suggested that twice as much time be

spent on each maths problem as for each other question.How many minutes should be spent on mathematics problems

A.36

B.72

C.60

D.100

Ans:B


16.In a group of 15,7 have studied Latin, 8 have studied Greek, and 3 have not studied either.How many of these studied both Latin and Greek

A.0 B.3 C.4 D.5

Ans.B


17.If 13 = 13w/(1-w) ,then (2w)2 =

A.1/4

B.1/2

C.1

D.2

Ans:C


18. If a and b are positive integers and (a-b)/3.5 = 4/7, then

(A) b < a

(B) b > a

(C) b = a

(D) b >= a

Ans: A


18. In june a baseball team that played 60 games had won 30% of its game played. After a phenomenal winning streak this team raised its average

to 50% .How many games must the team have won in a row to attain this average?

A. 12

B. 20

C. 24

D. 30

Ans: C


19. M men agree to purchase a gift for Rs. D. If three men drop out how much more will each have to contribute towards the purchase of the gift/

A. D/(M-3)

B. MD/3

C. M/(D-3)

D. 3D/(M2-3M)

Ans: D


20. A company contracts to paint 3 houses. Mr.Brown can paint a house in 6 days while Mr.Black would take 8 days and Mr.Blue 12 days. After 8

days Mr.Brown goes on vacation and Mr. Black begins to work for a period of 6 days. How many days will it take Mr.Blue to complete the contract?

A. 7

B. 8

C. 11

D. 12

Ans:C

21. 2 hours after a freight train leaves Delhi a passenger train leaves the same station travelling in the same direction at an average speed of

16 km/hr. After travelling 4 hrs the passenger train overtakes the freight train. The average speed of the freight train was?

A. 30

B. 40

C.58

D. 60

Ans: B

22. If 9x-3y=12 and 3x-5y=7 then 6x-2y = ?

A.-5

B. 4

C. 2

D. 8

Ans: D


23. There are 5 red shoes, 4 green shoes. If one draw randomly a shoe what is the probability of getting a red shoe

Ans: 5c1/ 9c1


24. What is the selling price of a car? If the cost of the car is Rs.60 and a profit of 10% over selling price is earned

Ans: Rs 66/-


25. 1/3 of girls , 1/2 of boys go to canteen .What factor and total number of classmates go to canteen.

Ans: Cannot be determined.


26. The price of a product is reduced by 30% . By what percentage should it be increased to make it 100%

Ans: 42.857%


27. There is a square of side 6cm . A circle is inscribed inside the square. Find the ratio of the area of circle to square.

Ans: 11/14


28. There are two candles of equal lengths and of different thickness. The thicker one lasts of six hours. The thinner 2 hours less than the

thicker one. Ramesh lights the two candles at the same time. When he went to bed he saw the thicker one is twice the length of the thinner one. How

long ago did Ramesh light the two candles .

Ans: 3 hours.


29. If M/N = 6/5,then 3M+2N = ?


30. If p/q = 5/4 , then 2p+q= ?


31. If PQRST is a parallelogram what it the ratio of triangle PQS & parallelogram PQRST .

Ans: 1:2


32. The cost of an item is Rs 12.60. If the profit is 10% over selling price what is the selling price ?

Ans: Rs 13.86/-


33. There are 6 red shoes & 4 green shoes . If two of red shoes are drawn what is the probability of getting red shoes

Ans: 6c2/10c2


34. To 15 lts of water containing 20% alcohol, we add 5 lts of pure water. What is % alcohol.

Ans : 15%


35. A worker is paid Rs.20/- for a full days work. He works 1,1/3,2/3,1/8.3/4 days in a week. What is the total amount paid for that worker ?

Ans : 57.50


36. If the value of x lies between 0 & 1 which of the following is the largest?

(a) x

(b) x2

(c) -x

(d) 1/x


Ans : (d)


37. If the total distance of a journey is 120 km .If one goes by 60 kmph and comes back at 40kmph what is the average speed during the journey?

Ans: 48kmph


38. A school has 30% students from Maharashtra .Out of these 20% are Bombey students. Find the total percentage of Bombay?

Ans: 6%


39. An equilateral triangle of sides 3 inch each is given. How many equilateral triangles of side 1 inch can be formed from it?

Ans: 9


40. If A/B = 3/5,then 15A = ?

Ans : 9B


41. Each side of a rectangle is increased by 100% .By what percentage does the area increase?

Ans : 300%


42. Perimeter of the back wheel = 9 feet, front wheel = 7 feet on a certain distance, the front wheel gets 10 revolutions more than the back

wheel.What is the distance?

Ans : 315 feet.


43. Perimeter of front wheel =30, back wheel = 20. If front wheel revolves 240 times. How many revolutions will the back wheel take?

Ans: 360 times


44. 20% of a 6 litre solution and 60% of 4 litre solution are mixed. What percentage of the mixture of solution

Ans: 36%


45.City A's population is 68000, decreasing at a rate of 80 people per year. City B having population 42000 is increasing at a rate of 120 people per year. In how many years both the cities will have same population?

Ans: 130 years

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