[SI-LIST] Re: Still looking for input ....
- From: "Nagel, Michael" <Michael.Nagel@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 31 Jan 2002 18:32:18 +0100
Weston,
I agree with your method in terms of function but want to add two things.
Measuring the flight time at the logic levels includes the effect of
dispersion,
especially at really high speed signals or very fast edges.
When the signal to noise ratio is poor the driver strength adds some errors
too
to the measured flight times.
Compromise:
Measuring the flight time at 50% of the signal amplitude for the properties
of the
printed crcuit board and measuring at the logic levels for design security.
Just my 2 cents ;-)
Michael
-----Original Message-----
From: Beal, Weston [mailto:weston_beal@xxxxxxxxxxx]
Sent: Donnerstag, 31. Januar 2002 18:17
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Still looking for input ....
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
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
