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Course contents

  • How to Use This Course
  • Low-Power Metrics Reference
  • Low-Power Glossary
  • Reading Path
  • Power Intent Fundamentals61
  • Isolation & Retention61
    • Isolation Strategies
    • Retention Register Design
    • Save/Restore Sequencing
    • Isolation Debug
    • Isolation & Retention: Tricky Q&A
  • Level Shifters & Power Switches61
  • UPF Implementation Flow61
  • Low Power Verification61
  • PD & Power Grid Integration61
  • Low Power Interview Prep4
  • Low Power / UPF Cheatsheet
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‹Low-Power Design
  1. Topics
  2. Low-Power Design
  3. Isolation & Retention

Low Power / UPF · All levels

Isolation & Retention

Isolation policies, retention registers, save/restore sequencing, and wake-up correctness under real mode transitions.

  • 5topics
  • 61lessons

Topics in this section

  1. 1Isolation Strategies15 lessons
    • Isolation Strategies: Mechanism
    • Isolation Strategies: Inputs & Outputs
    • Isolation Strategies: Reports & Metrics
    • Isolation Strategies: Debug Playbook
    • Isolation Strategies: Worked Example
    • Isolation Strategies: Pitfalls & Red Flags
    • Isolation Strategies: Interview Drills
    • Isolation Strategies: Review Checklist
    • Isolation Strategies: Theory Deep Dive
    • Isolation Strategies: Design Space
    • Isolation Strategies: Expanded Case Study
    • Isolation Strategies: Step-by-Step Walkthrough
    • Isolation Strategies: Comparison Matrix
    • Isolation Strategies: Software / Programmer View
    • Isolation Strategies: Silicon PPA Impact
  2. 2Retention Register Design15 lessons
    • Retention Register Design: Mechanism
    • Retention Register Design: Inputs & Outputs
    • Retention Register Design: Reports & Metrics
    • Retention Register Design: Debug Playbook
    • Retention Register Design: Worked Example
    • Retention Register Design: Pitfalls & Red Flags
    • Retention Register Design: Interview Drills
    • Retention Register Design: Review Checklist
    • Retention Register Design: Theory Deep Dive
    • Retention Register Design: Design Space
    • Retention Register Design: Expanded Case Study
    • Retention Register Design: Step-by-Step Walkthrough
    • Retention Register Design: Comparison Matrix
    • Retention Register Design: Software / Programmer View
    • Retention Register Design: Silicon PPA Impact
  3. 3Save/Restore Sequencing15 lessons
    • Save/Restore Sequencing: Mechanism
    • Save/Restore Sequencing: Inputs & Outputs
    • Save/Restore Sequencing: Reports & Metrics
    • Save/Restore Sequencing: Debug Playbook
    • Save/Restore Sequencing: Worked Example
    • Save/Restore Sequencing: Pitfalls & Red Flags
    • Save/Restore Sequencing: Interview Drills
    • Save/Restore Sequencing: Review Checklist
    • Save/Restore Sequencing: Theory Deep Dive
    • Save/Restore Sequencing: Design Space
    • Save/Restore Sequencing: Expanded Case Study
    • Save/Restore Sequencing: Step-by-Step Walkthrough
    • Save/Restore Sequencing: Comparison Matrix
    • Save/Restore Sequencing: Software / Programmer View
    • Save/Restore Sequencing: Silicon PPA Impact
  4. 4Isolation Debug15 lessons
    • Isolation Debug: Mechanism
    • Isolation Debug: Inputs & Outputs
    • Isolation Debug: Reports & Metrics
    • Isolation Debug: Debug Playbook
    • Isolation Debug: Worked Example
    • Isolation Debug: Pitfalls & Red Flags
    • Isolation Debug: Interview Drills
    • Isolation Debug: Review Checklist
    • Isolation Debug: Theory Deep Dive
    • Isolation Debug: Design Space
    • Isolation Debug: Expanded Case Study
    • Isolation Debug: Step-by-Step Walkthrough
    • Isolation Debug: Comparison Matrix
    • Isolation Debug: Software / Programmer View
    • Isolation Debug: Silicon PPA Impact
  5. 5Isolation & Retention: Tricky Q&A1 lesson
On this page

    Section goal

    Isolation policies, retention registers, save/restore sequencing, and wake-up correctness under real mode transitions.

    How to study this section

    1. Start with each topic hub and sketch the domain/state model.

    2. Use mechanism and reports pages to connect policy intent to evidence.

    3. Practice debug and worked-example pages for review readiness.

    4. Close with checklist and silicon impact before signoff discussions.

    Topics

    1. isolation-strategies/ — Isolation Strategies

    2. retention-register-design/ — Retention Register Design

    3. save-restore-sequencing/ — Save/Restore Sequencing

    4. isolation-debug/ — Isolation Debug

    Related topics

    • Low Power / UPF course hub

    Low-power deep dive

    Isolation and retention are sequence-sensitive contracts, not static checkboxes.

    Concept diagram

    Diagram
    SEQUENCE
    
    save -> isolate -> power-off -> power-on -> restore -> release

    Metric graph

    Diagram
    TRANSITION DEFECT MIX
    
    polarity errors      ███████
    late iso assertion   █████
    restore ordering     ████

    Reports and artifacts

    • isolation crossing report

    • retention list

    • save/restore timing

    • X-propagation log

    Mini case study

    A late isolation enable caused intermittent X leaks only on one PMU path.

    Debug branches

    • Validate control polarity

    • Trace AON source

    • Replay transition waveform

    Senior review question

    Ask: what transition evidence proves this topic is closed, and which owner signs it?

    Execution drill pack 1

    Use this pack to rehearse low-power closure on low-power/isolation-retention: transition framing, policy ownership, implementation evidence, and release confidence.

    Transition checklist

    • State transition explicitly named with legal source/target states.

    • Crossing and domain ownership are mapped and agreed.

    • Policy controls are traced to always-on source logic.

    • Waveform bookmarks align controls with state timestamps.

    Review prompts

    1. Which policy object is first to deviate from intent?

    2. Which owner can apply the smallest reversible fix?

    3. What regression matrix proves no collateral damage?

    4. Which waiver conditions would still block release?

    Evidence capsule

    Diagram
    LP EVIDENCE CAPSULE 1
    
    PATH: low-power/isolation-retention
    STATE WINDOW: <from -> to>
    POLICY OBJECT: <isolation / retention / shifter / switch>
    OWNER: <name>
    PRIMARY ARTIFACT: <report/waveform/formal result>
    RELEASE DECISION: <close / bounded waiver / escalate>

    Execution drill pack 2

    Use this pack to rehearse low-power closure on low-power/isolation-retention: transition framing, policy ownership, implementation evidence, and release confidence.

    Transition checklist

    • State transition explicitly named with legal source/target states.

    • Crossing and domain ownership are mapped and agreed.

    • Policy controls are traced to always-on source logic.

    • Waveform bookmarks align controls with state timestamps.

    Review prompts

    1. Which policy object is first to deviate from intent?

    2. Which owner can apply the smallest reversible fix?

    3. What regression matrix proves no collateral damage?

    4. Which waiver conditions would still block release?

    Evidence capsule

    Diagram
    LP EVIDENCE CAPSULE 2
    
    PATH: low-power/isolation-retention
    STATE WINDOW: <from -> to>
    POLICY OBJECT: <isolation / retention / shifter / switch>
    OWNER: <name>
    PRIMARY ARTIFACT: <report/waveform/formal result>
    RELEASE DECISION: <close / bounded waiver / escalate>

    Execution drill pack 3

    Use this pack to rehearse low-power closure on low-power/isolation-retention: transition framing, policy ownership, implementation evidence, and release confidence.

    Transition checklist

    • State transition explicitly named with legal source/target states.

    • Crossing and domain ownership are mapped and agreed.

    • Policy controls are traced to always-on source logic.

    • Waveform bookmarks align controls with state timestamps.

    Review prompts

    1. Which policy object is first to deviate from intent?

    2. Which owner can apply the smallest reversible fix?

    3. What regression matrix proves no collateral damage?

    4. Which waiver conditions would still block release?

    Evidence capsule

    Diagram
    LP EVIDENCE CAPSULE 3
    
    PATH: low-power/isolation-retention
    STATE WINDOW: <from -> to>
    POLICY OBJECT: <isolation / retention / shifter / switch>
    OWNER: <name>
    PRIMARY ARTIFACT: <report/waveform/formal result>
    RELEASE DECISION: <close / bounded waiver / escalate>

    Execution drill pack 4

    Use this pack to rehearse low-power closure on low-power/isolation-retention: transition framing, policy ownership, implementation evidence, and release confidence.

    Transition checklist

    • State transition explicitly named with legal source/target states.

    • Crossing and domain ownership are mapped and agreed.

    • Policy controls are traced to always-on source logic.

    • Waveform bookmarks align controls with state timestamps.

    Review prompts

    1. Which policy object is first to deviate from intent?

    2. Which owner can apply the smallest reversible fix?

    3. What regression matrix proves no collateral damage?

    4. Which waiver conditions would still block release?

    Evidence capsule

    Diagram
    LP EVIDENCE CAPSULE 4
    
    PATH: low-power/isolation-retention
    STATE WINDOW: <from -> to>
    POLICY OBJECT: <isolation / retention / shifter / switch>
    OWNER: <name>
    PRIMARY ARTIFACT: <report/waveform/formal result>
    RELEASE DECISION: <close / bounded waiver / escalate>

    Execution drill pack 5

    Use this pack to rehearse low-power closure on low-power/isolation-retention: transition framing, policy ownership, implementation evidence, and release confidence.

    Transition checklist

    • State transition explicitly named with legal source/target states.

    • Crossing and domain ownership are mapped and agreed.

    • Policy controls are traced to always-on source logic.

    • Waveform bookmarks align controls with state timestamps.

    Review prompts

    1. Which policy object is first to deviate from intent?

    2. Which owner can apply the smallest reversible fix?

    3. What regression matrix proves no collateral damage?

    4. Which waiver conditions would still block release?

    Evidence capsule

    Diagram
    LP EVIDENCE CAPSULE 5
    
    PATH: low-power/isolation-retention
    STATE WINDOW: <from -> to>
    POLICY OBJECT: <isolation / retention / shifter / switch>
    OWNER: <name>
    PRIMARY ARTIFACT: <report/waveform/formal result>
    RELEASE DECISION: <close / bounded waiver / escalate>
    PreviousNext: Isolation Strategies

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    See also

    • How to Use This Course
    • Low-Power Metrics Reference
    • Low-Power Glossary