Save/Restore Handshake Sequencing: Mechanism

Mechanism to understand

Mechanism for Save/Restore Handshake Sequencing is anchored on Handshake protocol compliance rate, save-to-off and restore-to-functional timing margin, and timeout escape count.. Convert observations into mechanism-backed and owner-bound actions.

Save/restore sequencing must be verified as a protocol, not only as a waveform snapshot. The environment should assert legal ordering between save request, save acknowledge, isolation enable, clock gating, power switch transitions, and restore deassertion. Verification should model realistic controller jitter, firmware delays, and concurrent requests from neighboring domains so sequencing robustness is validated under system pressure. Critical checks include ensuring restore is blocked until clocks and supplies are stable, retained state is visible before dependent logic resumes, and no stale handshake from a prior cycle leaks into the next power event. Negative tests should intentionally inject early wake, missing save ack, and double-trigger conditions to prove recovery paths and watchdog behavior instead of assuming clean operation.

• Name first boundary where expected transition behavior diverges.

• Prove mechanism with one high-confidence evidence packet.

• Assign owner for smallest reversible mitigation.

Execution flow

LOW-POWER VERIFICATION FLOW - Save/Restore Handshake Sequencing

power intent and mode definitions
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      v
domain controls and transition sequencing
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      v
simulation behavior (isolation, retention, corruption)
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      v
assertions and coverage evidence
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      v
triage, bounded fix, and signoff closure

Low-power verification deep dive

Retention closure requires proving end-to-end state lifecycle through save, off, and restore windows.

Concept diagram

RETENTION LIFECYCLE

save request -> state capture -> power off -> power on -> restore -> traffic resume

Metric graph

RETENTION STABILITY

restore mismatch       █████
save timing defects    ████
stable wake cycles     ███████

Metrics and artifacts to collect

• retention save/restore timing report

• pre/post state diff matrix

• multi-cycle retention stress summary

• state-loss bug trend by mode

Mini case study

A corruption issue persisted until retention checks compared multi-cycle state snapshots rather than single wake events.

Debug branches

• Track save acknowledgement against actual state capture.

• Validate restore completion before functional traffic resumes.

• Run repeated sleep/wake cycles to expose drift.

Senior review question

Ask: what exact low-power transition boundary failed first, and which artifact proves the closure claim reproducibly?

Key takeaways

• Tie each LPV claim to a concrete transition boundary and one proving artifact.

• Prefer minimal reversible fixes with explicit owner and rollback criteria.

Common pitfalls

• Treating power-aware failures as random before boundary classification.

• Waiving X-prop failures before proving impact and root cause.

• Declaring closure without deterministic replay across key modes.

Mechanism deep dive

Mechanism detail: Save/restore sequencing must be verified as a protocol, not only as a waveform snapshot. The environment should assert legal ordering between save request, save acknowledge, isolation enable, clock gating, power switch transitions, and restore deassertion. Verification should model realistic controller jitter, firmware delays, and concurrent requests from neighboring domains so sequencing robustness is validated under system pressure. Critical checks include ensuring restore is blocked until clocks and supplies are stable, retained state is visible before dependent logic resumes, and no stale handshake from a prior cycle leaks into the next power event. Negative tests should intentionally inject early wake, missing save ack, and double-trigger conditions to prove recovery paths and watchdog behavior instead of assuming clean operation.

Strong explanations tie transition semantics directly to observed failures.