RE: Drive-on-demand

Bob, DC, are you referring to the double drive devices like AVC logic, which
has fast drive in the 20-80% region and then softens the drive at the
corners? This is a technology we've wanted to evaluate for some time, but
the IBIS standard does not support it yet.
Regards,
Fabrizio Zanella
EMC corporation
fzanella@emc.com

-----Original Message-----
From: Bob Ross [mailto:bob_ross@mentorg.com]
Sent: Thursday, August 31, 2000 9:24 PM
To: ibis@lumbercartel.com
Cc: ibis-users@eda.org
Subject: Re: Drive-on-demand

D.C.:

Based on your description, I do not believe Bus_hold will work
directly. I do not believe simulators will work with
"negative" currents in the tables - meaning doing the
opposite of what is expected or creating a negative
impedance buffer that acts opposite of a conventional buffer.

Opposite polarity I-V tables will probably be flagged
as an error by the ibischk3 parser. Therefore it would
not be legal.

I cannot think of any clever alternative with IBIS
Version 3.2.

However, I believe the new macro language under discussion by
the IBIS Futures Working Group will be able to handle this
situation (this would be a good test case).

Bob Ross
Mentor Graphics

"D.C. Sessions" wrote:
>
> Need to double-check this. It seems that there are standard
> logic components which, on output, sense the output voltage
> and adjust drive current in response.
>
> No, I don't mean bus hold. These parts drive LOW hard when
> the output voltage is above a certain threshold and cut the
> drive when the output is below that threshold. Rising-edge
> drive is similar.
>
> Yes, I know that this is of dubious stability. Nobody asked
> me if they should do it this way, but the manufacturers want
> to make this a JEDEC standard and I'm trying to help them
> put together an IBIS model. Which, as far as I can tell, is
> possible using
>
> Submodel_type Bus_hold
>
> and having negative currents in the [Pulldown] and [Pullup]
> tables.
>
> 1) Have I missed a better way to do this?
> 2) Will this be legal?
> 3) Will this break EDA tools?
>
> --
> D. C. Sessions
> ibis@lumbercartel.com
 
Received on Thu Sep 7 05:27:37 2000