Multi-bit CDC Hazards: Reports & Metrics

Reports and metrics

Reports & Metrics for Multi-bit CDC Hazards focuses on data coherence violations, reconvergence warning count, escaped protocol bugs. The goal is to convert issue observations into mechanism-backed closure decisions.

Reports must explain risk movement in data coherence violations, reconvergence warning count, escaped protocol bugs, not just issue counts. A report is complete only when ownership and closure action are explicit.

Metric movement

METRIC TREND — data coherence violations, reconvergence warning count, escaped protocol bugs

critical open issues
  ^
  |                target (0 critical)
  |              - - - - - - - - - -
  |          o post triage
  |      o initial run
  |   o baseline
  +--------------------------------------> review iteration

Always pair count trend with evidence quality trend.

Risk distribution

RISK HEATMAP — Multi-bit CDC Hazards

severity
high   |  XX  X
medium |  XXX XX
low    |  XXX XXX
        +----------------------------> ownership readiness
         unassigned   in-progress   closed

Metric focus: data coherence violations, reconvergence warning count, escaped protocol bugs

• Track data coherence violations, reconvergence warning count, escaped protocol bugs by block, mode, and severity.

• Separate structural warnings from behavior-proven hazards.

• Show waiver age and owner SLA alongside raw counts.

• Store evidence links with each closure claim.

CDC/RDC deep dive

Metastability is managed risk, not eliminated risk.

Concept diagram

METASTABILITY FLOW

async event -> first sample may metastabilize
 -> settle window
 -> downstream sample confidence

Metric graph

MTBF TREND

target MTBF ---------
current design   ____/

Reports and artifacts

• MTBF assumptions

• synchronizer inventory

• crossing class summary

• critical waivers

Mini case study

Pulse sync chosen for a level signal caused intermittent stuck state under voltage stress.

Debug branches

• Validate crossing class first

• Check pulse width assumptions

• Audit synchronizer template usage

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.

Reading evidence