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Corner / Mode Matrix Design: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Corner / Mode Matrix Design.

Step-by-step analysis walkthrough

Use when you own Corner / Mode Matrix Design in a timing war room.

  1. Open signoff scenario list — note worst WNS corner.

  2. report_timing -max/-min on failing group.

  3. Trace launch and capture clocks on critical path.

  4. Check exceptions and generated clocks on path.

  5. Break down cell vs net delay.

  6. Compare implementation vs signoff view if delta suspicious.

  7. Assign owner: RTL, synth, PD, CTS, SI.

  8. Propose ECO with hold/SI check plan.

  9. Run regression matrix.

  10. Update closure dashboard and memo.

Artifacts to collect

  • MMMC scenario table, signoff matrix spreadsheet, scenario WNS dashboard

  • SDC file

  • SPEF tag

  • MMMC scenario list

  • ECO ticket

Decision memo template

diagram
STA DECISION MEMO — Corner / Mode Matrix Design
corner/mode:
WNS/TNS:
hypothesis:
ECO:
regression:
owners: STA lead, library owner, product architect

Reference visuals

MMMC scenario cube

diagram
MMMC MATRIX

           mode: func   test   low_power
corner ss     [ ]       [ ]      [ ]
       tt     [ ]       [ ]      [ ]
       ff     [ ]       [ ]      [ ]

Each checked cell = full STA run.
Signoff = worst WNS across all checked cells.

STA deep dive

Signoff WNS is the minimum across the full scenario matrix.

Concept diagram

diagram
MMMC

corners (ss/tt/ff) x modes (func/test) x views (signoff RC)
= scenario set -> min(WNS) is signoff

Metric graph

diagram
WNS HEATMAP BY CORNER

        ss    tt    ff
setup  -80   +10   +5
hold   -15   -2    -8

Reports and artifacts

  • per-corner WNS

  • mode summary

  • lib map audit

  • view delta

Mini case study

Passed TT typical but failed SS hold — signoff matrix was incomplete; added low-voltage mode.

Debug branches

  • Isolate failing scenario first

  • Never compare unlike SPEF tags

Senior review question

Ask: what corner/mode/view proves this topic is closed or failing?

Key takeaways

  • State corner, mode, view, and database tag with every slack claim.

  • Run setup and hold plus MMMC regression after every ECO.

Common pitfalls

  • Comparing STA runs with different SPEF or SDC tags.

  • Broad false_path to green-wash violations.

  • Setup-only ECO without hold check.

Principal STA review addendum

MMMC runs STA across PVT corners and functional modes; the matrix must cover real silicon without exploding runtime.

Metric: corner coverage completeness, mode cross-product size, signoff WNS per scenario

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