Pulse Synchronizers: Inputs & Outputs

Inputs and outputs contract

Inputs & Outputs for Pulse Synchronizers focuses on pulse miss rate, minimum pulse width margin, duplication events. 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.

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

CROSSING FLOW — Pulse Synchronizers

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

Key metric: pulse miss rate, minimum pulse width margin, duplication events

Ownership map

OWNERSHIP MAP — Pulse Synchronizers

artifact                  owner
----------------------    -------------------------
design intent           RTL owner
verification evidence   CDC owner
signoff decision        DV owner

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

CDC/RDC deep dive

Protocol correctness is the bridge between structural clean and functional safe.

Concept diagram

PROTOCOL FLOW

intent -> transport protocol -> synchronization -> destination acceptance

Metric graph

PROTOCOL ISSUE BURNDOWN

open issues: 20 -> 11 -> 5 -> 0

Reports and artifacts

• FIFO pointer proofs

• req/ack liveness

• pulse miss checks

• protocol assertions

Mini case study

Async FIFO empty/full logic looked correct until gray decode mismatch appeared during reset overlap.

Debug branches

• Pointer sync audit

• formal liveness checks

• reset interaction review

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

Pulse crossings require width expansion, toggle encoding, or ack-backed transport because short pulses can vanish between destination sampling edges.

Metric: pulse miss rate, minimum pulse width margin, duplication events