[SI-LIST] Re: HSPICE for 10Gbps link simulation?
- From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 10 Oct 2012 15:42:34 -0400 (EDT)
Chris,
You're entirely correct - which is why a full-on AMI model for the RX is
preferable. You have the ability to simulate millions of bits, model the
adaptive behavior of the equalizer and the interactions with the clock
recovery circuit.
My original response was based on "if all I have is an HSPICE model, then
...". In that case, I maintain an LTI approximation is better than no
analysis at all.
Engineering judgment applies, of course. The user has to be able to
understand the bounds of the result and how to apply it in practice.
Todd.
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. â www.sisoft.com
6 Clock Tower Place â Suite 250 â Maynard, MA 01754
(978) 461-0449 x24 â twesterh@xxxxxxxxxx
âI want to live like that â
-Sidewalk Prophets
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Cheng, Chris
Sent: Wednesday, October 10, 2012 2:42 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HSPICE for 10Gbps link simulation?
Having a FFE and DFE in HSPICE is only a small part of your analysis.
The output of the DFE is the slicer decisions which are ones and zeros, it
doesn't tell you anything about your channel margin nor it gives you any eye
diagram.
Your DFE slicer samples its input based on a lot of possible clocking way
including but not limited to CDR, phase interpreter or PLL. Have you ever
try to make a PLL dynamically locked to the reference phase in HSPICE ?
Let's just say you decided to use algo based AMI to simulated "millions of
cycles" as suggested below, how does the LTI work when the DFE is a dynamic
changing equalizer that alter the input according to previous output.
Let's just say you stick with full circuit cycle to cycle simulations. That
means you have to use some form of peak distortion to converge to worst case
patterns. How does that work when the DFE feedback alter the input according
to different post cursor patterns. How do you figure out what is the worst
case pattern then ?
I am just saying......
Chris Cheng
Distinguished Technologist , Electrical
Hewlett-Packard Company
+1 510 413 5977 / Tel
chris.cheng@xxxxxx / Email
4209 Technology Dr
Fremont, CA 94538
USA
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Todd Westerhoff
Sent: Wednesday, October 10, 2012 5:54 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HSPICE for 10Gbps link simulation?
Arpad,
In the scenario I described, the simulation time is longer, but not
significantly so.
For what it's worth, I'm doubtful that the vendor has been provided a
transistor-level model that models DFE equalization and adaptation in a
significant way. If so, it will be the first one I've seen.
Todd.
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. â www.sisoft.com
6 Clock Tower Place â Suite 250 â Maynard, MA 01754
(978) 461-0449 x24 â twesterh@xxxxxxxxxx
âI want to live like that â
-Sidewalk Prophets
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Muranyi, Arpad
Sent: Tuesday, October 09, 2012 11:50 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HSPICE for 10Gbps link simulation?
Istvan,
We can take the HyperLynx specific details off line, but for now, as you saw
it from Steve's reply, we do have the capability to run HSPICE as the
simulation engine from HyperLynx. If your vendor is willing to let you have
the unencrypted models, we could most likely even run them with our own
SPICE engine called Eldo for which you would not need to have the HSPICE
license. Or, if they are not willing to give you the unencrypted model
files we can send them an encryption utility and have them do the encryption
for Eldo and let them send you the Eldo encrypted files. We can work out
the details off line (even in Hungarian if you like)...
So is this HSPICE model for the Tx or the Rx? Considering that you
mentioned that it has FFE/DFE in it, I would think it is for the Rx.
Are you thinking of using an IBIS-AMI Tx model and use this HSPICE Rx model
on the other end of the channel? Did you run any simulations with this
HSPICE model to have an idea for how much time it needs for the simulations?
I wonder how long it would take to run a 1 million bit simulation and how
many ignore bits you need to throw away before you see a reasonable eye.
Regarding Todd's comments in this thread, while I agree that it is possible
to use an IBIS-AMI Tx model with the transistor Rx model, I wonder whether
the simulation time is prohibitively large. The linearization Todd
mentioned would not help to speed up the time it takes to push the waveforms
through the transistor level FFE/DFE logic, unless you find a way to
"convert" those to some sort of "behavioral" or "algorithmic" equivalents
and simulate them that way. But these types of conversions are not
necessarily easy or accurate, unless you are very familiar with what is
inside the transistor model and know what you are after.
Remelem, hogy beszelhetunk errol tobbet talan meg magyarul is...
Arpad
==================================================================
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Istvan Nagy
Sent: Tuesday, October 09, 2012 8:10 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HSPICE for 10Gbps link simulation?
Hi,
Thanks for the detailed explanations.
I have done some IBIS-AMI simulations a year ago on an ADS-trial version,
but I never had to deal with HSPICE so I didnt know anything about it.
I just found out few things:
-The HSPICE model we have has FFE/DFE in it, based on the pdf that came with
the model -Our vendor now provides IBIS-AMI models for the chip (which
should be supported by both ADS and Hyperlynx, We currently have
Hyperlynx) -Agilent ADS could simulate HSPICE models in certain cases, i
think it also needs HSPICE to be installed on the same PC. I didnt see any
sign of this support in Hyperlynx.
Todd, did you check out my LinkedIn profile today? -someone from your
company did.
Regards,
Istvan Nagy
Fortinet
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