CDC / RDC · All levels

Scenario: Metastability Bug: Inputs & Outputs

Inputs & Outputs for Scenario: Metastability Bug.

Inputs and outputs contract

Inputs & Outputs for Scenario: Metastability Bug focuses on root-cause depth, containment plan clarity, debug sequencing. The goal is to convert issue observations into mechanism-backed closure decisions.

Treat CDC/RDC signoff as a contract across architecture, RTL, DV, and signoff governance. Most late surprises are contract mismatches, not tooling gaps.

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INPUTS
  - crossing inventory with intent classification
  - reset tree and release dependency model
  - protocol assumptions and assertion package
  - CDC/RDC tool configuration + waiver policy

OUTPUTS
  - severity-tagged open issue list
  - protocol/reset proof evidence
  - owner-assigned closure plan
  - signoff or escalation memo

Crossing sequence

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CROSSING FLOW — Scenario: Metastability Bug

source clock domain -> launch signal -> crossing structure -> destination sample
      |                    |                 |                    |
   source FF           protocol           sync / fifo         destination FF

Key metric: root-cause depth, containment plan clarity, debug sequencing

Ownership map

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OWNERSHIP MAP — Scenario: Metastability Bug

artifact                  owner
----------------------    -------------------------
design intent           candidate
verification evidence   CDC owner
signoff decision        DV lead

Every open CDC/RDC issue needs one accountable owner before waiver or fix.

Scenario debrief

Score each response on mechanism clarity, evidence quality, and signoff decision discipline.

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INTERVIEW FLOW

classify -> explain mechanism -> propose fix -> state regression

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PRACTICE SCORE

session1 62%
session2 78%
session3 89%

Debrief prompts

Which crossing class or reset dependency failed first?
What evidence changed your decision?
Fix, waive, or escalate and why?

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