ASIC libraries Re: [SI-LIST] : IBIS models

John Fitzpatrick ([email protected])
Fri, 27 Aug 1999 10:06:19 -0700

The IBIS standard soes not *officially* cover one very important
application:
buffer libraries for ASICs or programmable devices.
.
IBIS library models are very useful for such questions as:
What package to use and how many pins?
Which buffer is best suited to a proposed topology?
What "Time of Flight" to use in system-level timing?
=> simulations are done *before* component is defined.

The usual workaround is to declare N fictive pins, one for each buffer
in the library.
This works well. What works less well is how to include parasitics for
different
package types - the different possible values are commented out.

John

Scott McMorrow <[email protected]> on 26/08/99 19:17:52

Please respond to [email protected]






To: [email protected]

cc: (bcc: John FITZPATRICK/FR/ALCATEL)



Subject: Re: [SI-LIST] : IBIS models

All,

Yep, it is generally standard laziness on the model makers
side. The logic goes like this:

1) all the i/o buffers on the device are exactly the same.
2) i have specified the min/max/typ package parasitics.
3) all i need to do is provide the data for one pin
4) the user can figure out the rest.

I hate doing this just as much as the rest of you. Fortunately
I have software to extract the pin mappings in IBIS format
of all parts in my simulation database. It is provided by my
simulator vendor. With this it is easy to fix the sins of
a poor model supplier.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com




Syed Huq wrote:


> Mike,
>
> You are correct. All pins should be specified under the [Pin] keyword.
> I have come across 'one' company that is consistently doing this. Most
> do provide a full [Pin] list.
>
> Regards,
> Syed
> Cisco Systems, Inc
>
> > X-SMAP-Received-From: outside
> > Date: Thu, 26 Aug 1999 08:47:52 -0500 (CDT)
> > From: Mike Mayer <[email protected]>
> > To: [email protected]
> > Subject: [SI-LIST] : IBIS models
> >
> > I have found several IBIS models that use the [Pin] keyword but only
> > model a couple of pins. For example, an octal buffer in a 20-pin
> > package that only includes statements for one buffer input pin, one
> > buffer output pin, Vcc and Gnd. My reading of the IBIS spec would say
> > that this is non-compliant. In Section 5 under "Usage Rules" for the
> > [Pin] keyword the first sentence states "All pins on a component must
> > be specified.".
> >
> > 1) Am I correctly interpreting the IBIS specification?
> >
> > 2) How common are models of this type?
> >
> > --
> > =============================================================================
> > Mike Mayer                               Artesyn Communication Products, Inc
> >                                          Madison, WI
> >                                          http://www.artesyn.com/cp
> > =============================================================================
> >
> >
> > **** To unsubscribe from si-list: send e-mail to [email protected].
> In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****
> >
>
> **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.  si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****


**** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.  si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****