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help:clock skew in Astro

Y

yyqonline

hi,
everyone
I meet a problem while using Asto to implete my deisgn. After Placement

& Routing, I find the clock path is between about 130ns to 220ns (a
specific, and very very slow lib used in my design) by using
"Timing=>Skew Analysis...", but while I check my timing path, I find
that Astro still consider the "clock network" is 1.000ns which is
specified in my ".sdc" file. In a other word, the clock skew are not
calculated when Astro calculats path timing. I have changed "Timing
Setup" options such as "ignore clock uncertainty", "ignore propagated
clock" after CTS. This results in problems while STA by PrimeTime.
For example, a path having a slack is 90ns in Astro Timing Report can
be negetive in PT which takes the clock skew into account.
Can anybody give some advice?
Thanks.

YuQing
 
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