Hardware interview practice
Cross a long-lived mode bit
A configuration bit changes rarely and remains stable for thousands of destination-clock cycles. The destination only needs its stable level, not the exact change cycle. What is the appropriate basic CDC circuit?
Choose one
Answer choices
- A. Synchronize every bit through one shared flip-flop so they all settle together.
- B. A combinational wire directly into destination logic because the bit changes rarely.
- C. Convert the bit to Gray code; a one-bit signal cannot use ordinary synchronizer flops.
- D. A two-flop level synchronizer in the destination domain, with the source required to remain stable long enough to be sampled.