Type-3: Give Verilog/VHDL code ...

Most Common Interview Questions: Type-3: Give Verilog/VHDL code ...

The prime intention of the interviewer in asking this question is to see the hands-on experience you have. If you have mentioned that you are familiar with Verilog/VHDL in your resume and attending an ASIC engineer post, then you can expect this question. This question usually comes after asking Type-1 and/or Type-2 questions (explained in previous posts). No interviewer starts with this type of question.

The common strategy followed is: initially you will be asked "Type-1: Design a ..." and then as an extension you will be asked to code it in Verilog or VHDL. Further, the interviewer may specifically ask you, to code for synthesis.

Tips

  • This question is asked to test your ability to code. Don't ever write a psuedo code or a code with syntax error(s).
  • Prepare for this question by coding some basic programs like flip-flops, counters, small FSMs etc. Make sure that you touch most of the commonly used Verilog/VHDL keywords.
  • Once you write some code, try to synthesize it and also try to find out the solution(s) if there are any errors.
  • Code some combinational and sequential codes. Try to code using hierarchies.
This is not a good way of testing one's knowledge, this is usually used to just see the hands-on experience you got. Sometimes this may become crucial if the project (which you are hired for) requires an ASIC design enginner urgently, so if you have enough experience then time can be saved by skipping training.

You might also want to read the following articles

Type-2: Tell us about a design/project you worked on

Type-1: Design a ...

First Things First -- Preparing a Good Resume

Type-2: Tell us about a design/project you worked on

Most Common Interview Questions: Type-2: Tell us about a design/project you worked on

Prepare for answering this question in any interview you attend, its kind of inevitable. Usually our resumes will be flooded with some projects. So an interviewer, instead of asking about one of those projects, he simply hits the ball into your court by asking this question. In general, interviewers ask to talk about your best work, it could be a design you made out of your interest or a project or part of a coursework. Irrespective of whether interviewer uses the word best its implied that you are going to talk about your best work! Now the ball is in your court you have to give a smart reply using your skills.

How to answer this question?

Remember that the time you have to answer this is limited. So instead of explaining every aspect of your design in detail, give glimpses of your design. Start taking about the best or challenging part of your design. This is best way of extracting some questions from interview which you can answer with ease. While you are explaining, the interviewer will most probably interrupt you and ask "why did you use this particular method? why not some other method?". In this case you are expected to give advantages of your design choice has, over other strategies. Failing to answer such questions will result in a very bad impression and ultimately rejection.

Example: Why did you use gray encoding for representing your FSM states? why not one-hot encoding? ... Here you have to know about one-hot encoding and the advantages that gray encoding has w.r.t. your design. If you are smart enough you can say that I considered various encoding techniques and chosen the best suited for my design. Don't forget to justify your statement. On the flip side if you say that I don't know one-hot encoding, the interviewer feels that your knowledge is limited and may also think that you have blindly followed your guides' instructions to use gray encoding.

Why is this question very important?

You should realize that you are just going to present something you already DID. In other questions you may require some time to think, solve or understand and you may get little tensed if you don't get a proper idea. But nothing like that in this question. As I said above the ball is in court and you should not make an unforced error!

All you have to do is use this question as your prime weapon to get the job!

You might also want to read the following articles

Type-1: Design a ...

First Things First -- Preparing a Good Resume

Type-1: Design a ...

Most Common Interview Questions: Type-1: Design a ...

This is the most common question one will face in his/her interview, probably the first question which starts testing your knowledge. (I mean this comes after introduction and "Tell us about yourself"). This is a lethal weapon used by the interviewer to test one's abilities: both weak and strong points. The concepts required for solving the problem are generally related to the type of job you are being tested for.

The most popular strategy used by the interview in this question is gradual increase in the complexity of the question. It goes like this ... Interviewer states the specifications of the design. You can present as simple/straight forward/redundant answer as possible. The next question could be redesign using only NOR gates or NAND gates. Followed by "what are minimum number of NAND gates required for this particular design" and it goes on.

Sometimes it starts with designing a small block. Then you will be asked to embed this module in a bigger picture and analyze the scenario. Where most likely you will face questions like "can the design (you made) be optimized for better performance of the entire module?" or "what drawbacks you see in your design when embedded in the bigger module". Basically tests how good you are with designs with a hierarchy.

Another way is step by step removal of assumptions that make the design complex as we go further.

Tips

  • Read the job description, think of possible questions or target areas, and prepare for the same.
  • ASIC interviews (especially freshers) expect a question dealing timing analysis, synthesis related issues, etc.

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