Re[2]: Interpretation of I/O data

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John,

Sorry that I didn't respond for so long, but I was very busy the last few weeks.
Here are my answers to your EMAIL:

>OK. My question was to confirm that the static I/V curve
>could be extracted from an IBIS file.
>I think so, but two cases are unclear for me (due
>to the lack of examples?): FAST-type inputs and Bus-hold inputs.

What are you referring to when you say FAST-type?
Shouldn't the Bus-hold circuit be modeled as an output rather than an input?

>If there is more than one power-supply, and one supply fails,
>it would be useful to predict the input impedance of an unpowered
>input buffer.

Inputs usually clamp below and above the supply rail. If the failing power
supply shorts to GND, the input will clamp below -0.6 volts and above +0.6
volts.

>Can a buffer which doesn't clamp when powered, clamp
>when unpowered (for applied voltages in the range 0 to Vcc)?

If the power on the input disables the clamping somehow, I can see that it could
clamp when it is not powered. But it would be helpful if you would state what
kind of input you are referring to. Regular CMOS, or something unusual, which I
don't know about? CMOS DOES clamp ewen when it is powered (0.6 volts above
Vdd).

>Then I have misunderstood the use for "Vinh" and "Vinl". Are these not
>used to decide if a simulated signal is acceptable or not? Specifying
>the minimum hysteresis would correctly allow noisier signals to pass,
>(this is often the reason for choosing a buffer with hysteresis).

These two keywords are not there to define the hystereris.

>I'd hope a simulator would warn me if any signals risk crossing
>a threshold too slowly.

Valid point, but there is no keyword in IBIS yet to base this warning on. If it
is important to you, you might want to raise this (and the hysteresis) issue in
the Open Forum Meeting. I brought it up last time, and people are open to these
kinds of comments, requests.

Sincerely,

Arpad
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References: <Thu,.14.Dec.95.08:45:07.PST_12@ccm.hf.intel.com>
Subject: Re: Interpretation of I/O data
To: Arpad Muranyi <Arpad_Muranyi@ccm.fm.intel.com>
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Date: Thu, 14 Dec 1995 19:59:27 +0100
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