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Course contents

  • How to Use This Course
  • Reading Path
  • CDC/RDC Glossary
  • CDC/RDC Metrics Reference
  • CDC/RDC Interview Prep
  • CDC/RDC Signoff Cheatsheet
  • Clock Domains and Failure Modes8
  • Metastability and Synchronizers16
  • CDC Protocols and Handshakes16
  • Reconvergence and Gray Coding16
  • Reset Domain Crossing16
  • Architecture and Design Rules16
  • CDC Signoff Methodology24
  • RDC Signoff16
  • Debug and Case Studies11
  • CDC and RDC Interview Prep30
    • CDC/RDC Whiteboard Framework
    • CDC/RDC Framework Drills
    • Scenario: Metastability Bug
    • Scenario: Metastability Escape in Silicon Bring-up
    • Scenario: Async FIFO Pointer Mismatch
    • Scenario: Waiver Debate
    • Scenario: RDC Waiver Under Tapeout Pressure
      • The Scenario
      • What You Would Do
      • Communicating the Risk
    • CDC/RDC Interview Q&A Bank
    • CDC/RDC Interview Q&A Bank (Expanded)
  • Capstone: Sign Off a Multi-clock Peripheral4
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‹Scenario: RDC Waiver Under Tapeout Pressure
  1. Topics
  2. CDC & RDC
  3. CDC and RDC Interview Prep
  4. Scenario: RDC Waiver Under Tapeout Pressure
  5. What You Would Do

Part 10 · Interview Prep · All levels

What You Would Do

The 36-hour triage: refresh intent, re-analyse the variant, then fix, evidence, conditional waiver, or refuse per item.

With the piles sorted, spend the hours where they change verdicts. Refresh the reset intent against the three ECOs first, with the block owners in one room: no intent, no verdicts. Re-run the analysis against the variant's reset order, since that is the sequence the original signoff never checked. Then disposition each item into exactly one of four outcomes.

Outcome

When

Needs

Fix now

Defective release synchronisation on a sequenced reset.

An RTL edit plus re-analysis; admit the milestone slips for these rather than waiving them.

Waive with evidence

Current intent, clean re-analysis, and reset-aware simulation of the item's sequences.

The evidence package attached to the waiver, reviewed, with expiry.

Conditional waiver

Evidence exists for the main variant but not the odd one.

Scope the waiver to the checked variants and flag the unchecked one as a known open risk.

Refuse

Designer statement only, or stale intent that cannot be refreshed in time.

A written refusal with the containment: hold the milestone item open, do not sign.

Expect the count to be uncomfortable: perhaps a handful waived, several conditional, and the rest refused or deferred. That distribution is the point. A triage that waives all twenty in 36 hours did not triage; it surrendered. Say which items you would fix even at the cost of the milestone, because reset release defects are boot failures, and boot failures are respins. The review-gate language for this stance is Pre-Tapeout Gates.

Common pitfall

Splitting the difference: waiving the medium items to "show progress" while refusing only the highs. Severity labels computed against stale intent are unreliable, so the split point is arbitrary. Disposition by evidence per item, never by label.

Check yourself An item has clean simulation but its intent row predates an ECO touching its reset. Waive, fix, or refuse?

Refuse until intent is refreshed and analysis re-run: the simulation exercised a design the ECO may have changed, so its evidence is stale regardless of how green it looks.

Related topics

  • Next: Communicating the Risk

  • Hierarchical RDC

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