Detecting Redundant or Missing Isolation: Software and Programmer View

Software and programmer view

Crossing failures are often specification and ownership mismatches between logic and intent teams.

What teams feel

• mode-entry regressions that are hard to reproduce

• inconsistent behavior across simulators or config profiles

• late triage loops due to weak failure classification

API and integration impact

• PMU and firmware handshake contract clarity

• power-mode API assumptions and timing envelopes

• testbench sequencing ownership and checker placement

Tooling and compile-time implications

• tool power-aware semantics and elaboration assumptions

• assertion noise versus actionable signal quality

• coverage aggregation consistency across runs

Mitigations

• standardize LPV run metadata and transition sequence capture

• gate key regressions on deterministic replay checks

• enforce boundary ownership in review templates

SOFTWARE VIEW - Detecting Redundant or Missing Isolation
// prove phase ordering and boundary controls before broad waivers

Low-power verification deep dive

Boundary correctness depends on timing: isolate and shift at the right crossings and right phases.

Concept diagram

BOUNDARY SAFETY VIEW

domain crossing -> level-shift requirement -> isolation control -> OFF/ON transition behavior

Metric graph

BOUNDARY BUG CLASSES

missing isolation      █████
late isolation         ████
LS misdirection        ███

Metrics and artifacts to collect

• cross-domain boundary inventory

• clamp-value correctness report

• LS direction and threshold checks

• missing or redundant boundary action list

Mini case study

A boundary bug escaped unit tests until domain-off traffic stress revealed late isolation enable timing.

Debug branches

• Map each crossing to expected LS and isolation behavior.

• Verify enable timing against collapse and restore edges.

• Check clamp safety for protocol-facing signals.

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.

Principal LPV review addendum

Detecting Redundant or Missing Isolation should be reviewed as a transition integrity system, not just isolated checks.

Use Missing-isolation high-severity findings and redundant-cell area/timing overhead eliminated before low-power signoff freeze. as alarm and Risk-ranked crossing ledger showing missing, justified-exempt, and redundant isolation candidates with closure action and waiver evidence. as proof.

Isolation and level-shifting quality is measured at crossing correctness, clamp safety, and timing of control intent. Closure quality comes from reproducible evidence and explicit owners.