FSM Encoding and Its PPA Impact: Binary vs Gray vs One-Hot | VLSI Interview Question

Binary, Gray or one-hot: how does FSM state encoding actually change the power, performance and area of a synthesized design, and when does each one win? 🎯 In this video • The three encodings compared: binary uses the fewest flops (4 for 10 states) with up to 4 bits flipping per transition; Gray keeps the same flop count but flips only 1 bit on sequential steps; one-hot needs one flop per state (10) but exactly 2 bits flip per transition • Measured synthesis results: binary comes in at 45 gates / depth 8 / 20,795 state toggles; Gray drops to 38 gates / depth 7 / 17,794 toggles; one-hot with full comparisons jumps to 84 gates / depth 11, while a proper one-hot style next-state equation cuts that back to 26 gates / depth 4 • When each encoding wins: binary for large machines (dozens of states) where area and scan matter most; Gray when transitions mostly step to the next state, for lower switching power; one-hot for small and medium machines where speed and decode simplicity matter ⏱️ Chapters 0:00 Interview Question: FSM Encoding and PPA 1:11 The Three Encodings 2:46 Measured Results 4:31 When Each Encoding Wins 5:36 Recap 🚀 Preparing for an ASIC / VLSI / digital design interview? This lecture is one of many in my Udemy course, Mastering ASIC VLSI Digital Design Interviews: clear, step-by-step explanations of the questions hiring managers actually ask, plus the follow-ups that catch candidates off guard. 👉 Get the full course at a discounted price with coupon ASIC2026: https://www.udemy.com/course/masterin... 👍 If this helped, like and subscribe for more digital VLSI interview prep, and share it with a friend who's interviewing! #PPA #FSM #VLSI #DigitalDesign