[SI-LIST] Re: On time to vm
- From: "Jon Powell" <jonpowell@xxxxxxxxxxxx>
- To: <Lakshmi_s@xxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 11 Mar 2004 07:47:01 -0800
Dear S.
A negative delay (with VM correction enabled) implies that the signal gets
from the driver to the receiver FASTER than the databook spec part delay
driver drives the test load (which used to be a 50pf load).
This sort of delay only makes sense if you are doing timing verification and
using the CLK to Out (or internal delay) in the part that is specified using
a test load driving to the measurement voltage (Vm).
If you look up TIME_TO_VM or Vm correction in the XTK manual you should find
a lot more information.
I wrote a white paper on the subject that should be available through Mentor
support also (I looked and I don't have it anymore.. sorry).
Min and Max delay represents time (rising) to the low threshold (min) and to
high threshold (max). You can get very long time differences if you have
oscillation around a threshold (which will also register as an error).
take care (enjoy XTK)
jon
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Lakshmi S - CTD,
Chennai.
Sent: Thursday, March 11, 2004 4:15 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] On time to vm
Hi,
Pre route SI Analysis using XTK gives negative minimum delays and positive
maximum delays. There is a large variation between the two (Ex :
-0.493ns(min delay) and 0.55ns(max delay)). I've enabled vm correction.
As I want to know just the trace delay from the driver to the receiver, I do
not understand whether to enable time to vm correction.
Could anyone please clarify ?
Thanks and regards,
S. Lakshmi
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