[SI-LIST] Re: Still looking for input ....

For most fast parts, manufacturers guarantee timing at a reference voltage and 
a minimum slew rate. In such cases, using Vil/Vih levels for timing results in 
double counting.

Regarding simulators reporting slew rates, this information can be indirectly 
obtained by having the simulator report Vil/Vih crossing times.

Thanks,
Vinu

"Beal, Weston" wrote:

> Todd,
>
> Maybe the silence is an admission of lack of knowledge.  In my dealings with 
> various hardware designers, some of them want the measurements done one way 
> or the other, but the reason is usually something like, "That's the way RJ 
> always does it."  From all my understanding, I believe that the correct 
> method is to measure at the logic thresholds.  This statement also assumes 
> that we've done our very best to correctly model all the parts of our circuit 
> that we can.  If the circuit works correctly at the corner cases then it's 
> almost guaranteed to work over the range of manufacturing tolerances.  
> Measuring to one reference voltage at the receiver doesn't tell you anything 
> about the performance of the circuit after manufacturing.
>
> Later,
> Weston
>
> -----Original Message-----
> From: Todd Westerhoff [mailto:twester@xxxxxxxxxxx]
> Sent: Thursday, January 31, 2002 8:18 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Still looking for input ....
>
> Okay, folks ...
>
> So far we've seen two posts to my question of how flight times are measured.
>
> Since we've seen substantial discussion recently on questions related to
> higher education and Physics 101, I was REALLY hoping to see some more
> discussion on this particular SI issue.
>
> One line responses with a vote are fine.  One line responses saying "your
> question doesn't make sense!" are even OK.  But silence is NOT golden in
> this case.
>
> Thanks!
>
> Todd.
>
> Todd Westerhoff
> SI Engineer - Hammerhead Networks
> 5 Federal Street - Billerica, MA - 01821
> email:twester@xxxxxxxxxxx - ph: 978-671-5084
> ============================================
>
> "Oh, but ain't that America, for you and me
>  Ain't that America, we're something to see
>  Ain't that America, Home of the Free
>  Little pink houses, for you and me"
>
> - John Mellencamp
>
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