Microprocessor and Microcontroller Interview Questions: A complete question bank with real-time examples

By Anita Gehlot

Book gives you a complete idea about the Microcontroller and Microprocessor. It starts from a very basic concept like a number system, then explains the digital circuit. This book is a complete set of interview questions and answers with plenty of screenshots. Book takes you on a journey to Microprocessor 8085, Peripheral Devices and Interfacing, AVR ATmega32, Interfacing of Input/Output Device.
Book also covers the descriptive questions, multiple-choice questions along with answers which are asked during an interview.

• Language: English
• Publisher: BPB Online LLP
• Release date: Feb 12, 2020
• ISBN: 9789389845082

Book preview

CHAPTER 1

Number Systems

Introduction to Number systems

Number systems are used to reparesent the information in various systems. Electronic and Digital systems may use a variety of different number systems, (Decimal, Hexadecimal, Octal, Binary).

A number N in base or radix b can be written as:

(N)b = dn-1 dn-2 — — — — d1 d0. d-1 d-2 — — — — d-m

In the above:

dn-1 to d0 is integer part

follows a radix point

d-1 to d-m is fractional part.

Here:

dn-1 = Most significant bit (MSB)

d-m = Least significant bit (LSB)

Binary number system

The binary number system is another way to represent quantities. The binary number has only two digits 0 and 1.

Weight structure of a binary system is:

2n-1……….2³ 2² 2¹2⁰. 2-1 2-2 2-3 ……. 2-n

Where:

n: The number of bits from the binary point

.: Binary point

2: Base of binary number system.

Example: (11011)2

Octal number system

The number system whose base is 8 is known as the octal number system. The base 8 means the system uses eight digits from 0 to 7. The next digit in octal number is represented by 10, 11, 12, 13, 14, 15, 16, 17 which represents the decimal digits 8, 9, 10, 11, 12, 13, 14, 15.

Weight structure of an octal system is:

8n-1……….8³ 8² 8¹8⁰. 8-1 8-2 8-3 …….. 8-n

Where:

n: positional of octal number system

. : Octal point

8: Base of octal number system.

Example: (745)8

Decimal number system

The number system whose base is 10 is known as the decimal number system. The base 10 means the system uses ten digits from 0 to 9.

Weight structure of a decimal system is:

10n-1…………10³ 10² 10¹ 103⁰. 10-1 10-2 10-3 …….. 10-n

Where:

n: positional of Decimal number system

. : Decimal point

10: Base of Decimal number system.

Example: (7459)10

Hexadecimal (hex) number system

The number system whose base is 16 is known as the Hexadecimal number system. The base 16 means the system uses ten digits from 0 to 9, A – F.

Weight structure of a decimal system is:

16n-1…………16³ 16² 16¹16⁰. 16-1 16-2 16-3 …….. 16-n

Where:

n: positional of Hexadecimal number system

. : Hexadecimal point

16: Base of Hexadecimal number system.

Example: (75AC)16

The table 1.1 shows the decimal, binary, octal, and hexadecimal numbers from 0 to 15 and their equivalent binary number.

Table 1.1: Number system equivalent

Complement

Complements are used in digital computers to simplify subtraction. The complements are classified in two types based on the number systems base.

r’s complement or Radix complement.

(r-1)’s complement or diminished complement.

r’s complement

If N is a positive number to base r with integer part of n digit, the r’s complement of N is defined as rn – N.

r’s complement = rn – N

Where:

r: base of the number system

n: number of integer digit

N: given positive number

Or

r’s complement = (r-1)’s complement + 1

Question 1.1: Find 2’s complement of 11011 binary number

No of integer digits = 5

(r-1)’s Complement

If N is a positive number in base r with n integer digits and m fraction digits, (r-1)’s complement is defined as:

[(rn– 1) – N] or (rn – r-m - N)

Where:

r: base of the given number system

n: number of integer digits

N: given positive number

m: number of fraction digits

Question 1.2: Find 1’s complement of 10110 binary number.

Number of integer digit = 5

Number Conversion

Binary to Decimal conversion

Steps:

Write the binary number

Write the weights 2⁰ 2¹ 2² 2³ etc., under the binary digits starting with the bit on right hand side.

Cross out weights under zeros

Add the remaining weights.

Question 1.3: Convert the given binary number into decimal number (10011)2 = (?)10

First, multiply all the digits in the number by 2 and add them:

(1*2) + (0*2) + (0*2) + (1*2) + (1*2)

Give powers to 2 starting from 0 from right to left.

(1*2⁴) + (0*2³) + (0*2²) + (1*2¹) + (1*2⁰)

That’s all the formula part.

Now, convert the powers of 2 to the numbers.

(1*16) + (0*8) + (0*4) + (1*2) + (1*1)

Summing up all, gives the answer as:

16 + 0 + 0 + 2 + 1 = 19

So, (19)10 is the decimal equivalent of the given binary number (10011)2.

Question 1.4: Convert the given binary number into decimal number (110111)2 = (?)10

So, (55)10 is the decimal equivalent of the given binary number (110111)2.

Question 1.5: Convert the given binary number to decimal number (1101)2 = (?)10

Question 1.6: Convert the given binary number to decimal number (1011.101)2 = (?)10

Split non-fractional part and fractional part

Non fractional part: (1011)2

Fractional part: (.101)2

Binary to decimal conversion for non-fractional part

(1*2³) + (0*2²) + (1*2¹) + (1*2⁰)

= 8 + 0 + 2 + 1

= (11)10

Binary to decimal conversion by putting negative power for fractional part

(1*2-1) + (0*2-2) + (1*2-3)

= (1* 1/2) + 0 + (1*1/8)

= (1/2) + (1/8) = 5/8 = 0.625

So, we got (0.625)10, which is the decimal equivalent of the binary fraction (.101)2. Therefore, the decimal form of the binary number (1011.101)2 is (11.625)10.

Binary to octal conversion

Question 1.7: Convert the given binary number to decimal number (10111101)2 = (?)8

In this the given number is grouped in bits of threes, and then each group is converted to its decimal.

101 ➔ 5

111 ➔ 7

010 ➔ 2

So, (275)8 is the octal equivalent of the given binary number (10111101)2.

Question 1.8: Convert the given binary number to decimal number (1011100011)2 = (?)8

In this the given number is grouped in bits of threes, and then each group is converted to its decimal.

011 ➔ 3

100 ➔ 4

011 ➔3

001 ➔ 1

So, (1343)8 is the octal equivalent of the given binary number (1011100011)2.

Binary to Hexadecimal conversion

Question 1.9: Convert the given binary number to Hexadecimal number (1011100011)2 = (?)16

In this the given number is grouped to bits of fours, and then each group is converted to its Hexadecimal.

0011 ➔ 3

1110 ➔ 14 ➔ E

0010 ➔ 2

So, (2E3)16 is the Hexadecimal equivalent of the given binary number (1011100011)2.

Question 1.10: Convert the given binary number to Hexadecimal number (111001100011101)2 = (?)16

In this the given number is grouped to bits of fours, and then each group is converted to its Hexadecimal.

1101 ➔ 13 ➔ D

0001 ➔ 1

0011 ➔ 3

0111 ➔ 7

So, (731D)16 is the Hexadecimal equivalent of the given binary number (111001100011101)2.

Decimal to Binary conversion

Question 1.11: Convert the given decimal number to binary number (548)10 = (?)2

In this conversion, we divide the decimal number continuously by 2, note down its remainder and continue with the dividing of number until the quotient get 0.

We have to take (write) down to up as MSB to LSB correspondingly.

So, (1000100100)2 is the Binary equivalent of the given decimal number (548)10.

Question 1.12: Convert the given decimal number to binary number (41.68)10 = (?)2

For fractional part:

For fractional decimal numbers, multiply it by 2 and record the carry in the integral position.

For integral part is remaining same:

For fractional part:

For fractional part we need take (Write) from top to bottom.

So, (101001. 10101..)2 is the Binary equivalent of the given decimal number (41.68)10.

Decimal to octal conversion

Question 1.13: Convert the given decimal number to octal number (458)10 = (?)8

In decimal to octal conversion, number is continuously divided by 8 and the remainder is recorded until the quotient is 0.

So, (712)8 is the Octal equivalent of the given decimal number (458)10.

Decimal to Hexadecimal conversion

Question 1.14: Convert the given decimal number to Hexadecimal number (458)10 = (?)16

In decimal to hexadecimal conversion, number is continuously divided by 16 and the remainder is recorded until the quotient is 0.

So, (1CA)16 is the Hexadecimal equivalent of the given decimal number (458)10.

Octal to Binary conversion

Question 1.15: Convert the given octal number to binary number (472)8 = (?)2

In octal to binary conversion, number can be converted to