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Reset Deassertion CDC: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Reset Deassertion CDC.

Step-by-step analysis walkthrough

Use this sequence when owning Reset Deassertion CDC in a signoff review.

  1. Inspect warning class and severity.

  2. Trace crossing endpoints and domains.

  3. Check protocol/reset assumptions against spec.

  4. Review synchronizer or FIFO implementation detail.

  5. Run focused assertion or formal check.

  6. Draft fix options with risk and schedule impact.

  7. Execute regression and publish closure memo.

Artifacts to collect

  • reset tree map, release synchronizer audit, RDC report

  • crossing inventory

  • waiver board notes

  • regression report

Decision memo template

diagram
CDC/RDC DECISION MEMO — Reset Deassertion CDC
risk class:
mechanism:
evidence:
fix/waiver:
owners: reset architect, CDC owner, RTL owner

Reference visuals

Async assert, sync release

diagram
reset_n (global) ----> assert immediately
                  |
                  +--> per-domain release synchronizer

Unsynchronized deassertion can metastabilize startup flops.

CDC/RDC deep dive

Reset release ordering is a first-order reliability contract.

Concept diagram

diagram
RESET RELEASE FLOW

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

Metric graph

diagram
BOOT STABILITY

passes per 1k boots: 920 -> 980 -> 999

Reports and artifacts

  • reset dependency matrix

  • RDC warning classes

  • boot stress logs

  • waiver aging

Mini case study

Domain B released before producer A was valid, causing rare startup deadlock.

Debug branches

  • Correlate reset and clock timelines

  • verify async assert/sync release

  • exercise skewed release tests

Senior review question

Ask: what evidence proves this risk is closed for silicon, not just tool-clean?

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.

Principal CDC/RDC review addendum

Asynchronous assertion is usually safe, but reset deassertion must be synchronized per destination domain to prevent uncertain startup state capture.

Metric: reset release violations, metastability-on-release risk, boot instability

Practice this lesson