DenseChip

AMS Interface · All levels

Sample Timing Contract: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Sample Timing Contract.

Step-by-step analysis walkthrough

Use this when you own Sample Timing Contract during an AMS war room.

  1. Capture failing mode and environmental condition.

  2. Pull synchronized waveform, logs, and report artifacts.

  3. Mark first boundary where legal behavior diverges.

  4. Audit reset/clock/power sequence assumptions.

  5. Check physical coupling contributors (floorplan/power/package) where relevant.

  6. Assign single-thread ownership for the first fix.

  7. Propose bounded change and define success criterion.

  8. Run scenario and safety regressions.

  9. Document findings in closure memo.

  10. Update signoff dashboard and waiver state.

Artifacts to collect

  • timing contract table, phase alignment report, calibration captures

  • handoff contract

  • firmware/config tag

  • physical signoff snapshot

  • decision memo

Decision memo template

diagram
AMS DECISION MEMO — Sample Timing Contract
mode/condition:
metric:
hypothesis:
fix:
regression:
owners: system architect, timing owner, ADC/DAC owner

Reference visuals

Sampling contract

diagram
sample edge alignment + aperture budget + CDC boundary
=> valid digital sample interpretation

AMS deep dive

Wrapper and sampling contracts determine data trustworthiness.

Concept diagram

diagram
CONVERTER DATA FLOW

sampling clock -> wrapper -> sync boundary -> system consumer

Metric graph

diagram
INVALID SAMPLE BURSTS

time --->  _|¯¯|__|¯¯¯|____|¯|_

Reports and artifacts

  • sample validity ratio

  • calibration convergence

  • CDC audit

  • overflow/stale sample counters

Mini case study

Mode transition changed sample phase and invalidated wrapper framing assumptions.

Debug branches

  • Sample timing contract

  • Calibration hook behavior

  • Wrapper CDC integrity

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.

Principal AMS review addendum

Sampling quality depends on clock phase relationships, aperture uncertainty, and synchronization boundaries between converter clocks and system clocks.

Metric: aperture budget compliance, sample alignment error, control-loop jitter

Practice this lesson