Low Power / UPF · All levels
Retention Register Design: Step-by-Step Walkthrough
Step-by-Step Walkthrough for Retention Register Design.
Step-by-step analysis walkthrough
Use when you own Retention Register Design in a low-power closure war room.
Open failing LP test and capture transition window.
Map source/destination domains and state at failure point.
Check isolation/retention/level-shifter policies on that crossing.
Verify PMU ordering against spec.
Check implementation reports for physical legality.
Run root-cause branch: intent vs sequence vs physical.
Patch minimal owner-controlled change.
Run focused test then full LP matrix.
Update signoff dashboard and closure note.
Artifacts to collect
retention list, save/restore controller spec, and retention verification report
UPF revision
PMU sequence trace
state coverage report
waiver ledger
Decision memo template
LOW-POWER DECISION MEMO — Retention Register Design
state transition:
observed metric:
root cause:
fix:
regression:
owners: RTL owner, UPF owner, design verification ownerReference visuals
Retention datapath
RETENTION FLOP MODEL
functional FF ----save----> retention latch (AON rail)
functional FF <---restore-- retention latch
retention_supply must remain alive through collapse.Low-power deep dive
Isolation and retention are sequence-sensitive contracts, not static checkboxes.
Concept diagram
SEQUENCE
save -> isolate -> power-off -> power-on -> restore -> releaseMetric graph
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?
Key takeaways
State transition context must accompany every low-power metric claim.
Intent changes require simulation, formal, and implementation re-validation.
Common pitfalls
Comparing results from mismatched UPF revisions.
Assuming static checks replace transition validation.
Shipping with aged waivers and unclear ownership.
Execution drill pack 1
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 1
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 2
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 3
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 4
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 5
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 6
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 6
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 7
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 7
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 8
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 8
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 9
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 9
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 10
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 10
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 11
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 11
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 12
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 12
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
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 13
Use this pack to rehearse low-power closure on low-power/isolation-retention/retention-register-design/step-by-step-walkthrough: 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
Which policy object is first to deviate from intent?
Which owner can apply the smallest reversible fix?
What regression matrix proves no collateral damage?
Which waiver conditions would still block release?
Evidence capsule
LP EVIDENCE CAPSULE 13
PATH: low-power/isolation-retention/retention-register-design/step-by-step-walkthrough
STATE WINDOW: <from -> to>
POLICY OBJECT: <isolation / retention / shifter / switch>
OWNER: <name>
PRIMARY ARTIFACT: <report/waveform/formal result>
RELEASE DECISION: <close / bounded waiver / escalate>Principal LP review addendum
Retention flops preserve selected state through power collapse by copying data into retention latches powered by an always-on supply.
Metric: retention coverage %, restore mismatch count, and retained state corruption escapes