Welcome to the ASIC and SoC Insider inside the interview series. In this episode, we’re talking about functional versus code coverage. The question that trips candidates up coverage always comes up in interviews, and the question that often trips people up is. What is the difference between functional coverage and code coverage?
For context on this question, this isn’t just about definitions. Interviews, want to see if you can tie coverage to verification, quality, risk management, and tape out confidence. So one of the questions you’ll face is explain the difference between functional coverage and code coverage.
An example of the answer would be code coverage is structural.
It measures how much of the RTL code has been executed during the simulation -statement coverage, branch coverage, toggle coverage, etc. It answers, did we exercise the code?
Functional coverage is specification driven. It measures whether the intended scenarios defined in the verification plan were exercised.
For example, during the NVMe project, we had 96% coverage. The functional coverage revealed that they never tested power state transitions. That gap would’ve been invisible if we’d only looked at the structural coverage.
Together they give you a complete view code coverage ensures execution breadth, Functional coverage ensures a requirement, validation missing either of these leaves a risk on the table. The risk translates to potential silicon re-pins, which can cost millions to a client. Strong candidates connect coverage to business impact confidence at a tape out and reduced chance of costly rework.
If you wanna stand out in your interviews, practice framing answers both technical depth or business value, reach out if you’d like more guidance on this. I’ve trained many different types of engineers, architects and directors across the UK, Europe, and the US.
This is the ASIC and SoC Insider. Let’s get started.
