( ESNUG 251 Item 7 ) -------------------------------------------- [9/12/96]
Subject: ( ESNUG 250 #3 ) Need Control Of Synopsys SDF File Generation
> The problem is that Synopsys writes out an SDF file where all three timing
> parameters (min/typ/max) are identical because it calculates the delays
> based on the last "set_operating_conditons" command. ... We want to write
> one SDF file where "min" delays are calculated w/ "best_case_commercial"
> operating conditions, "typ" delays are made from "typical_case" operating
> conditions, and "max" delays are calculated with "worst_case_conditions".
From: "David C. Black" <dblack@ink.apple.com>
John,
This user should be careful about using min/max values for ASIC simulations.
It may not be valid to run a min/max simulation depending on the type of
min/max data you use.
There are two types of min/max. First, there is overall prodcut min/max as
considered over temperature, voltage, and process. Second, there is single
device min/max within a single part for a specified operating condition. A
min/max spread for with a single chip will be very small; whereas, it is
quite large for a chip to chip comparison.
Simulating one gate running fast at 5.5v and 110 degF on one corner of the
die with another running slow at 4.5v and -10 degF can be quite erroneous.
This is probably the reason Synopsys takes this approach.
On the other hand, it is nice to be able to quickly running an entire
simulation at min, and then run another simulation at max. Using two files
is perhaps a hassle, but maybe safer in Synopsys' view.
- David C. Black
Apple Computer
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