CDC / RDC · All levels

Reset Domain Crossing: Tricky Q&A

Senior interview and review questions for Reset Domain Crossing.

Section Q&A bank

Use these drills after completing all topics in Reset Domain Crossing. Answer with crossing class, mechanism, risk, evidence, owner, and signoff decision.

Why is reset deassertion the risky phase?

diagram

[INT][CDC-RDC][RESET-DOMAIN-CROSSING]

Q: Why is reset deassertion the risky phase?

A:
Assertion forces known state, while deassertion re-enters sequential behavior and can metastabilize destination flops if unsynchronized.

FOLLOW-UP TRAP: Assuming async reset means async release is always safe.

What does reset sequencing prevent?

diagram

[INT][CDC-RDC][RESET-DOMAIN-CROSSING]

Q: What does reset sequencing prevent?

A:
Bring-up races where consumers run before producers or clocks are stable.

FOLLOW-UP TRAP: Using one global reset pulse with no dependency model.

When is RDC waiver acceptable?

diagram

[INT][CDC-RDC][RESET-DOMAIN-CROSSING]

Q: When is RDC waiver acceptable?

A:
Only with mechanism rationale, containment proof, ownership, and expiry for revalidation.

FOLLOW-UP TRAP: Waiving due to schedule urgency alone.

Q&A drill guide

diagram

INTENT -> FAILURE MODE -> EVIDENCE -> FIX/WAIVER -> REGRESSION

Sketch while answering

diagram

RESET RELEASE FLOW

assert global -> clocks stable -> sync release per domain -> first transaction

Key takeaways

State crossing class, assumptions, and owner with every issue.
Run structural and dynamic regressions after each fix.

Common pitfalls

Treating all warnings as equivalent risk.
Waiving issues without containment evidence.
Skipping reset and reconvergence stress after CDC fixes.

Practice this lesson