[SI-LIST] Re: Eye diagram measurement
- From: "Jeremy Plunkett" <jeremy@xxxxxxxxxxxx>
- To: janton@xxxxxxxxxxxxx, scott@xxxxxxxxxxxxx, edpc108@xxxxxxxxx
- Date: Thu, 7 Apr 2005 19:23:29 -0700
Jim,
Here is a trick that worked well for me. It complicates your spice deck a
bit but simplifies the post processing greatly.
Most of the time you don't need to know exactly how many failures occurred
if there were a lot of them. You are targeting 0 eye violations and if any
occurred then something is really wrong(most likely with the setup of your
buffer netlist). Maybe if you are simulating a marginal channel you would
be interested whether there were 10 failures or just one, but you certainly
don't care if 50% of the bits failed because that means something is
seriously wrong with your spice deck.
In this case you really only need 10 measure statements to capture the times
of the 1st 10 failures, and maybe another 10 to capture the voltage at each
failure so you can see in the spreadsheet what edge of your eye mask the
failures are occuring on.
The way to get just these 10 measurements is to build a "behavioral
receiver" that measures the difference between your differential waveform
and a waveform representing the mask(which you create with a pulse source),
and triggers a measurement based on the crossings. To simplify the mask
down to a single waveform, rectify the differential signal you're looking at
before comparing it. By having the mask waveform maintain a negative value
during times outside of the window you want to measure, you can avoid
triggering measurements at those times. An E element(voltage controlled
voltage source) works for the differential receiver, and an E element with
ABS=1 serves as the rectifier.
If you want to see the mask in a graphical eye diagram, you'll need a
separate mask waveform that covers both the positive and negative
requirements for the eye (one cycle pos-neg is enough, it can sit at 0 the
rest of the time). If you want to see the mask in a regular waveform plot,
you'll need 2 waveforms so both pos and neg limits are present in each bit
cell.
Best regards,
Jeremy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Jim Antonellis
Sent: Wednesday, April 06, 2005 8:15 AM
To: scott@xxxxxxxxxxxxx; edpc108@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Eye diagram measurement
Hi Scott, Jaaprakash,
I looked into this a while back, and I thought using the HSPICE .MEASURE
construct you did not have the ability to make multiple bit cell
measurements. Could you please share the .MEASURE syntax that would make
this possible as I had to resort to a post-proc spreadsheet last time I did
it.... and would greatfully appreciate the "trick".
Thx,
Jim
-
Jim Antonellis janton@xxxxxxxxxxxxx
Sandburst Corp www.sandburst.com
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On
Behalf Of Scott McMorrow
Sent: Wednesday, April 06, 2005 11:12 AM
To: edpc108@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Eye diagram measurement
Jaaprakash,
Yes. It can be done with .measure statements, or it can be done with
SiSoft's SiAuditor measurement capability.
scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
TeraspeedR is the registered service mark of
Teraspeed Consulting Group LLC
Jayaprakash wrote:
> Hi ,
>
> Is it possible to measure eye diagram height and
>width (not graphically) in HSPICE simulations?
>
> Thanks,
>
> Best regards,
> Jayaprakash.
>
>
>
>Send instant messages to your online friends
>http://uk.messenger.yahoo.com
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