Reports and metrics

Reports & Metrics for Jitter Budgeting focuses on total jitter budget, deterministic/random split, downstream timing margin. The goal is to connect observed symptom to boundary mechanism, ownership, and signoff risk.

Reports convert total jitter budget, deterministic/random split, downstream timing margin into release decisions. A single average metric is insufficient; use tails, mode breakdowns, and trend under controlled conditions.

Metric movement

METRIC GRAPH — total jitter budget, deterministic/random split, downstream timing margin

health / margin
  ^
  |                         target
  |                       - - - - - - -
  |                  o post-fix
  |              o
  |         o baseline
  |    o failing run
  +--------------------------------------> debug iteration
    repro setup    root-cause proof    release candidate

Readout:
  - compare only equivalent mode, payload, clock, and environment tags
  - separate symptom stabilization from true mechanism closure

Distribution view

METRIC DISTRIBUTION — Jitter Budgeting

occurrence
  |      ***
  |    *******
  |  ***********
  |*************  <- left tail (worst boundary excursions)
  +--------------------> margin / stability / error metric
  bad                 nominal

Fix the tail first; average value can hide integration escapes.

• Track total jitter budget, deterministic/random split, downstream timing margin by mode and stress condition.

• Report p95/p99 or worst-case tail when intermittent escapes matter.

• Store metric with exact artifact and configuration tags.

• Separate symptom stabilization from mechanism closure.

AMS deep dive

Clock quality evidence must include jitter and sequencing, not lock status alone.

Concept diagram

CLOCKING FLOW

reference -> PLL/DLL -> distribution -> endpoint margin

Metric graph

JITTER TREND

jitter ps
  ^
  |   o baseline
  |      o stress mode
  |         o failure edge

Reports and artifacts

• jitter budget

• lock/unlock counters

• phase-noise snapshot

• STA uncertainty deltas

Mini case study

False-lock condition released reset early; endpoint logic sampled unstable clock edge patterns.

Debug branches

• Lock qualification policy

• Reset sequencing check

• Package/supply contributors

Senior review question

Ask: what boundary condition proves this topic is actually closed?

Key takeaways

• State boundary, mode, and evidence tag with every claim.

• Always align analog, digital, and physical owners before signoff decisions.

Common pitfalls

• Fixing averages while tails still fail.

• Skipping package/supply evidence in jitter or SerDes issues.

• Shipping with waivers that lack owner and expiration criteria.

Reading reports