Setup / Hold Closure Order: Inputs & Outputs

Inputs and outputs contract

Inputs & Outputs for Setup / Hold Closure Order focuses on setup WNS, hold WNS, simultaneous violation count. The goal is to connect the observable symptom to timing mechanism, ownership, and regression risk.

Treat these as a signed interface contract. Ambiguity here is the single biggest source of wasted integration weeks, because two teams debug against different assumptions.

INPUTS
  - SDC (clocks, IO delays, exceptions)
  - Liberty libraries per corner
  - SPEF/parasitics and RC corner
  - MMMC scenario definition

OUTPUTS
  - WNS/TNS reports per scenario
  - path group summaries
  - constraint audit / waiver log
  - signoff closure memo

Timing path sequence

TIMING PATH — Setup / Hold Closure Order

launch FF --logic stages--> capture FF
     |                           |
  launch clock                capture clock
     |                           |
  required: arrival < capture_edge - setup
  metric: setup WNS, hold WNS, simultaneous violation count

Ownership map

OWNERSHIP MAP — Setup / Hold Closure Order

artifact              owner
----------------      -----------------
timing report       timing closure lead
SDC/constraint      PD owner
implementation      STA owner

Every WNS cluster needs a named owner before ECO.

STA deep dive

ECO without regression is a coin flip.

Concept diagram

ECO LOOP

failing path -> fix -> setup check -> hold check -> SI -> MMMC matrix

Metric graph

ECO PROGRESS

WNS
 0 |              o target
-50|        o
-100|   o baseline
    +-----------------> ECO #

Reports and artifacts

• pre/post WNS

• hold delta

• leakage delta

• ECO ticket log

Mini case study

48-hour tapeout crunch: VT swap fixed setup; hold fixed with route on short path — order mattered.

Debug branches

• Never ship setup-only proof

• Logical ECO needs equivalence

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

Setup and hold compete through delay changes; closure order and ECO type must avoid fixing one at the expense of the other.

Metric: setup WNS, hold WNS, simultaneous violation count