Interview Questions

Top 10 Microcontroller Interview Questions and Answers

Intel Corporation launched 8-bit microcontroller in 1981 known as 8051. It has earned huge fame and name when Intel incorporated a lot of manufacturers to market and produces different versions of 8051. They asked the manufacturers to make sure that their processors they remain compatible with the code of 8051. It has led to a lot of versions of 8051 with varied speeds and optimizations.

Even though there are many 8051 features in terms of speed and on-chip ROM, it is vital for you to keep in mind that they all are compatible with the original 8051. If you write any program, it means it will run on any program despite the manufacturer. So these things explain how important is a Microcontroller. If you are appearing for a Microcontroller Interview you must have a good knowledge about it. So in this article, we will discuss the frequently asked Microcontroller Interview questions and answers. Before that let’s have a look at the tips to answer these Microcontroller Interview questions.

Tips to get success in Microcontroller Interview

  • Research the Company and the Job – Take your time to research the company as well as the position you are going to interview. The more you know, the better you are prepared to respond to these questions.
  • Know the Facts – It seems like a no-brainer. But there are many candidates who cannot remember their work year and place. Be sure to consider your work history and also bring another copy of resume as a reference if you need a reminder and nervous.
  • Practice, Practice, Practice – The more you practice, the more comfortable you will be. Ask a family member or friend for help. Answer common questions asked during an interview to know how to respond.
  • Take Your Time – Don’t rush to get a response to the question. Think of your response before answering briefly. Take your time to compose your answers so you can answer well, rather saying something you didn’t wish after that.
  • Be Sure to Stay Calm – Interviewing can be fearful, be it your first interview or you have experience in interviewing several times in the past. Take enough time for you to visit the interview. Exercising breathing before you enter the room and do your best to keep calm.
  • Use Power Words – Make sure to use words that can convey your impression to the hiring manager during job interviews. You can make a good impression with your power words in response.
  • Stay Professional – Your responses should be based on your professional abilities and skills. You don’t have to tell about your interests, personal life, your hobbies or your family background unless they ask you. Also don’t tell about your work issues you might have like arranging transportation, child care, etc. after getting the job.
  • Use Examples – Explain with examples as for how you handled specific situations while responding to interview questions. You need to be more specific so hiring manager will see that you have specific skills for the job.

Microcontroller Interview Questions & Answers

Which Architecture Does Intel 8051 Follow?

Harvard Architecture

Tell me the difference between von Neumann Architecture and Harvard Architecture?

Harvard Architecture is named after Harvard Mark. The beauty of Harvard Architecture is that it has storage code, physically different signals, and data memory. One can access both data memory and access program memory at the same time. Usually, the data memory is read-write and program or code memory is read-only. So, program contents cannot be modified by the program.

John von Neumann is the early computer scientist, a great mathematician, and a mastermind behind von Neumann Architecture. These machines have shared memory and signals for data and code. Hence, the program can be modified easily since it is based on read-write storage.

Which Technology was used in Developing 8051?

NMOS Technology was used to develop the original MCS-51 from Intel family. But CMOS technology was used to develop later versions which are named with C series (e.g. 80C51) and save more power than NMOS technology. This way, they are best suited for battery-operated devices.

Why Intel 8051 is known as 8-bit microcontroller?

Most of the operations available are limited to 8 bits. This is the reason Intel 8051 is an 8-bit microcontroller.

What’s the width of address bus and data bus?

Data bus is 8-bit and address bus is 16-bit.

What are the features of 8051 microcontroller?

  • 128-byte RAM
  • 40 Pin IC
  • 4K ROM
  • 32 I/O pins
  • 2 Timers (Timer 1 and Timer 0)
  • 6 Interrupts
  • 1 serial port

What is known as on-chip RAM?

Direct Memory

Where data memory space and code memory space start?

At 0x00 location for external or internal memory

How much on-chip RAM allotted for data storage?

From location 0x00 to 0x7F, 128 bytes of RAM is allotted for data storage

How many instructions for 2 machine cycle and 1 machine cycle it can execute on per second basis, with 12 MHz of clock rate?

Actually, a cycle is 12 pulses of crystal. In case it takes one machine cycle for instruction to execute, it is believed that it will take 12 pulses to execute a crystal. As it is clear that crystal pulses at 11,059,000 times per second and 12 pulses are taken by one machine cycle, we can find out how many cycles 8051 can take per second –

i.e. 11,059,000/12 = 921,583

It means 8051 can conduct 921,583 instructions (single-cycle) per second.  Since a lot of 8051 instructions are single-cycle ones, it is often known that 8051 can conduct around 1 million instruction every second, even though it is less-and in reality, according to the instructions which have been used, around 600,000 instructions are more realistic on per second wise.


P.S. – Again, it is vital to mention that not all the instructions conduct at the same time. One machine cycle or 12 crystal pulses are the fastest instructions required, while several other instructions need 24 crystal pulses or two machine cycles and two slow operations need 48 crystal pulses or four machine cycles.

These are some of the frequently asked Microcontroller Interview questions and answers which you can consider preparing before you appear for the interview.

About the author

Atish Ranjan

Hi there, I am Atish Ranjan! I have been into work and business for more than 11 years now; I have given and taken numerous interviews over the years.
Thus, I started to share my knowledge & experience with you! Hope you enjoy reading here.

About the Author

Hi there, I am Atish Ranjan! I have been into work and business for more than 11 years now; I have given and taken numerous interviews over the years. Thus, I started to share my knowledge & experience with you! Hope you enjoy reading here.