Re: VINH and VINL

>>>> Howdy, My comments look like this >>>>> , Don Telian
>>>> Jon Powell's original memo follows....

Fellow IBIS type persons,

At the recent IBIS phone call I volunteered to author a BIRD on the
subject of requiring VINH and VINL specifications for input devices.
This was to avoid the problem of useless but IBIS legal input devices
with no logic threshold. Upon studying the problem I noticed that there
is actually a larger change required than I had anticipated and I
believe I should solicit comments before I actually write the BIRD.
The problem is two fold:

First. I believe that our current model-types are not sufficiently
exclusive. We have INPUT OUTPUT I/O 3-STATE and OPEN_DRAIN. Under
what category does a 3-state I/O fall?

>>>>> If it's "i/o", it's got to be "3-state", unless it intends
>>>>> to only drive itself. Right? Consequently, "3-state I/O"
>>>>> and "I/O" are the same thing.

Second. Do we wish to be able to model devices that are not any of these
above things but are still simple reasonable devices. like:

        Resistor Packs
        Termination Diode Packs
        Discrete 2 port devices

>>>>> This makes a lot of sense. And I think if we're clever we
>>>>> can do this with just a couple new "Model_type"s.

I believe we need a slight extension of the allowed model-types and then
a different way of being able to distinguish between OUTPUTS, INPUTS,
and LOADS.

>>>>> not sure what you mean here... But sounds like a good BIRD.

comments are requested.

jonp@qdt.com
Received on Thu Oct 7 16:47:58 1993