[SI-LIST] Re: measuring final settle time in HSPICE
- From: "Jeremy Plunkett" <jeremy@xxxxxxxxxxxxxxx>
- To: mike@xxxxxxxxxxx, 'si_list' <si-list@xxxxxxxxxxxxx>
- Date: Mon, 24 Sep 2001 21:28:07 -0700
Mike,
personally I favor the "brute force" approach of measuring the 1st,2nd,3rd,
and 4th crossing at each expected edge location. If there is a
non-monotonicity on the edge, I will catch 3 crossings and have the choice
of which one to consider for timing purposes (or consider that the end of my
solution space). If my measurement detects 4 crossings (all at that edge
location, not later), I know I have a serious problem and need to change the
bus topology if I want that case to work.
On busses which cannot tolerate any non-monotonicity, you only have to look
at 2 crossings (since 2 crossings indicates a failing case), and on busses
which tolerate lots of ringing, you may need to capture several.
The LAST option is not too useful since I am always interesting in the
timing across several cycles on the bus.
I'm hoping to hear how others have solved the same problem, since the method
above leads to rather large output files (tricky to load into excel).
Regards,
Jeremy Plunkett
Signal Integrity Engineer
ServerWorks Corporation
jeremy@xxxxxxxxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Mike LaBonte
Sent: Monday, September 24, 2001 1:01 PM
To: si_list
Subject: [SI-LIST] measuring final settle time in HSPICE
When performing a setup time check it is necessary to use the latest
time that the data signal becomes stable. On a low to high transition,
for example, this is conventionally the last time where the received
signal rises above Vinh and stays above. In the best case this will be
the first crossing. But ringing may necessitate 2 or more crossings
before the signal becomes stable enough to be latched.
How does one automate the measurement of this final settle time value in
HSPICE? The .measure statement lets you find the LAST crossing time for
a signal, but the time at which HSPICE begins to count data crossings is
either a fixed time value, or it is triggered by another signal. The
trigger signal could almost be the clock, but that signal obviously
changes too late to be the trigger. Has anyone found a convenient method
for automating these measurements?
Mike LaBonte
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