[ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI

From: "wkatz@xxxxxxxxxx" <wkatz@xxxxxxxxxx>
To: dan.dvorscak@xxxxxxxxx
Date: Tue, 17 Jul 2012 13:10:55 -0400 (EDT)
No. The model would need IV data to account for the impedance of the driver.

Walter

Sent from my Verizon Wireless 4G LTE DROID

Dan Dvorscak <dan.dvorscak@xxxxxxxxx> wrote:

Hi all,

Sorry to reply late to this thread.  I had been keeping an eye out for it,
but seem to have missed it.

Per what Greg and Arpad were discussing, should it not be up to the model
writer to decide whether or not an ideal or an IBIS-generated impulse
response is to be used?  My expectation would be that a given IBIS buffer
that points to an AMI model will contain all of the IBIS analog model
features that the model writer intends to be included in the channel
characterization.  In that sense if a user or EDA tool chooses to ignore
any of those features they are using the model in a way that it was not
characterized for.

Another way to look at it would be to say that if a model writer intended
for a model to work with an ideal impulse response, they
could essentially ship and IBIS file that pretty much only contains a
c-comp, "zeroed out" V-I tables, and sharp edge rate in the ramp data to
make it a fairly ideal driver.

Does that seem like a fair assessment?

Thanks,

-Dan


On Wed, Jul 11, 2012 at 10:37 AM, Muranyi, Arpad
<Arpad_Muranyi@xxxxxxxxxx>wrote:

>  Greg,****
>
> ** **
>
> The IBIS specification is intentionally silent about****
>
> how to generate the impulse response for the channel,****
>
> because there are different ways to do it, and EDA****
>
> vendors might want to use their own “smarts” to do it****
>
> the “best” way.****
>
> ** **
>
> You are correct, if someone wants to extract such an****
>
> “ideal” IR, you would only make use of the C_comp and****
>
> the impedance provided by the I-V curve from the analog****
>
> model.****
>
> ** **
>
> BIRD 120 doesn’t give any more detail (or restrictions)****
>
> on how to generate the impulse response.  So the EDA tool****
>
> is free to do it the way they think it is the best to do****
>
> it.****
>
> ** **
>
> I hope this helps,****
>
> ** **
>
> Arpad****
>
> ===========================================================****
>
> ** **
>
> *From:* ibis-macro-bounce@xxxxxxxxxxxxx [mailto:
> ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Gregory R Edlund
> *Sent:* Wednesday, July 11, 2012 9:15 AM
> *To:* 'IBIS-ATM'; ibis-macro-bounce@xxxxxxxxxxxxx
>
> *Subject:* [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI**
> **
>
>  ** **
>
> What if an EDA programmer wanted to discard the VT and ramp data and
> compute an "ideal mathematical" impulse response assuming a delta function?
>  Is that allowed by BIRD 120?  I took a quick look and didn't see anything
> specific about how to calculate the impulse response.  In the "ideal
> mathematical" case, I would think all you need is C_Comp and some
> resistance extracted from the IV tables.
>
> Greg Edlund
> Senior Engineer
> Signal Integrity and System Timing
> IBM Systems & Technology Group
> 3605 Hwy. 52 N  Bldg 050-3
> Rochester, MN 55901
>
>
>
> [image: Inactive hide details for "Walter Katz" ---07/11/2012 03:53:30
> AM---I agree.]"Walter Katz" ---07/11/2012 03:53:30 AM---I agree.
>
> From: "Walter Katz" <wkatz@xxxxxxxxxx>
> To: <Arpad_Muranyi@xxxxxxxxxx>, "'IBIS-ATM'" <ibis-macro@xxxxxxxxxxxxx>
> Date: 07/11/2012 03:53 AM
> Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI
> Sent by: ibis-macro-bounce@xxxxxxxxxxxxx****
>  ------------------------------
>
>
>
>
> I agree.
>
> Walter
>
> *From:* ibis-macro-bounce@xxxxxxxxxxxxx [
> mailto:ibis-macro-bounce@xxxxxxxxxxxxx <ibis-macro-bounce@xxxxxxxxxxxxx>]
> *On Behalf Of *Muranyi, Arpad*
> Sent:* Tuesday, July 10, 2012 11:44 PM*
> To:* IBIS-ATM*
> Subject:* [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI
>
> That is correct.
>
> Arpad
> ================
>
> *From:* ibis-macro-bounce@xxxxxxxxxxxxx
> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mirmak, Michael*
> Sent:* Tuesday, July 10, 2012 6:07 PM*
> To:* Walter Katz*
> Cc:* IBIS-ATM*
> Subject:* [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI
>
> Walter,
>
> Thank you!  So, someone using IBIS-AMI models with valid traditional data
> in a workflow should expect changes in the IBIS TX C_comp or V-t (or
> [Ramp]) data to have an impact on the results provided by the receiver in
> an IBIS-AMI-based flow, assuming nothing else changes?
>   ****
>
> -          MM****
>
>
> *From:* Walter Katz [mailto:wkatz@xxxxxxxxxx] *
> Sent:* Tuesday, July 10, 2012 12:20 PM*
> To:* Mirmak, Michael*
> Cc:* IBIS-ATM*
> Subject:* What part of Legacy IBIS is used by IBIS-AMI
>
> MM,
>
> The Legacy part of an IBIS model is used to generate the Impulse Response
> of the channel.
>
> One method of generating the impulse response is to do a step response,
> and take the derivative of the waveform at the Rx input.
>
> A simulator uses a combination of the Tx [Voltage Range], C_Comp, IV, VT
> and Ramp data, and the Rx C_Comp and IV data. Of course, [External Model]
> can also be used by a simulator.
>
> The following required Tx IBIS fields are not used in the AMI flow: ****
>
> Vmeas****
>
> The following required Rx IBIS fields are not used in the AMI flow: ****
>
> Vinl
> Vinh****
>
>
> Walter
>
>
> Walter Katz
> wkatz@xxxxxxxxxx
> Phone 303.449-2308
> Mobile 303.335-6156
>  ****
>



-- 
Daniel Dvorscak
ANSYS, Inc.
67 South Bedford St.
Suite 202E
Burlington, MA 01803
Tel:  781.229.8900 x352
Fax: 781.229.8624
[ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI

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