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Matt Venn

03/30/2023, 1:55 PM
Does anyone know how OpenLane's default
IO_PCT=0.2
is derived? (Specifies the percentage of the clock period used in the input/output delays. Ranges from 0 to 1.0)
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Dario Quintero

03/30/2023, 2:20 PM
Maybe this sheds some light? Matt Liberty posted this STA document a few days ago. Page 203 https://vlsitesting.files.wordpress.com/2017/02/ref-for-unit6.pdf
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Vijayan Krishnan

03/30/2023, 2:45 PM
Yes 20% applied by default.
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Matt Liberty

03/31/2023, 2:17 PM
If you use too small a value then you get lots of hold buffering around the inputs. 0.2 is just a heuristic value to avoid that. If you have a more realistic set of constraints you should prefer them
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Matt Venn

03/31/2023, 4:29 PM
thanks
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Tobias Strauch

04/01/2023, 5:25 AM
@Matt Liberty Sure about that (the hold buffering) ? It's a max constraint, not a min.