( ESNUG 342 Item 2 ) --------------------------------------------- [2/03/00]
From: Kayla R Klingman <kayla.r.klingman@tek.com>
Subject: Do NOT Use "set_dont_touch_network" On Clocks With DC 99.10 !!
Hi, John,
We found a bug in DC 99.10 where:
1) You clock on the negedge of the clock
2) You have a constant as the data in to a flop
3) And your clock has set_dont_touch_network on it
It would add buffers to the clock, even though you told DC to leave it
alone. The answer that came back from R&D at Synopsys was:
Get rid of the set_dont_touch_network on your clock.
In DC 99.10 they started assuming an ideal clock, so set_dont_touch_network
was redundant. They got rid of the set_dont_touch_network and the extra
clock buffering went away. We're still waiting to hear why we have
dangling gates, but simplify_constants -boundary_optimization gets rid of
them.
- Kayla Klingman
Tektronix, Inc. Oregon
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