[ibis-macro] Re: Terminator Model_type and *input* Algorithmic Models?
- From: Mike LaBonte <mike@xxxxxxxxxxx>
- To: Bob Ross <bob@xxxxxxxxxxxxx>
- Date: Sat, 5 Jan 2013 12:27:20 -0500
BIRD148 has:
The topic was discussed in the IBIS ATM Task Group teleconference on
> November 1, 2011 and the decision was made to add verbiage to the IBIS
> specification to disallow the usage of [Algorithmic Model] in Series,
> Series_switch and Terminator Model_types.
The referenced ATM meeting minutes are at http://tinyurl.com/aj664lh,
and it does appear that we agreed to drop Terminator as a model that
might have [Algorithmic Model], partly because a Terminator can be
referenced by a [Series Pin Mapping] to terminate two pins, which
might already have AMI models assigned.
Another consideration is that Model_type is used by EDA tools to
decide at the system level which pins to stimulate as drivers and
which to monitor as logic receivers with time and voltage quality
requirements. From it's introduction, Model_type Terminator was
ignored by tools as a logic receiver, simply to reduce superfluous
monitoring, and unclutter reports.
So even if Terminator seems potentially usable as an analog model for
AMI, I think it's role helping to decide which pins to analyze is more
important, and that would be lost if Terminator became practically
synonymous with Input. But one question is what will simulators do
during channel characterization with two diff pins that have Input AMI
models with no analog data, combined with a [Series Pin Mapping]
Terminator model that has the analog model but no AMI?
Mike
On Fri, Jan 4, 2013 at 9:44 PM, Bob Ross <bob@xxxxxxxxxxxxx> wrote:
> Michael:****
>
> ** **
>
> Some reasons were given in BIRD148.****
>
> ** **
>
> Bob****
>
> ** **
>
> *From:* ibis-macro-bounce@xxxxxxxxxxxxx [mailto:
> ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mirmak, Michael
> *Sent:* Friday, January 04, 2013 6:22 PM
> *To:* IBIS-ATM (ibis-macro@xxxxxxxxxxxxx)
> *Subject:* [ibis-macro] Terminator Model_type and *input* Algorithmic
> Models?****
>
> ** **
>
> A simple question (I specialize in those): why are we prohibited from
> using Model_type Terminator and [Algorithmic Model] together? The
> specification explicitly limits Terminator to input buffers, but that
> should only prevent using the Model_type with transmitters. Wouldn’t
> Terminator be a pretty friendly way of modeling receiver buffer analog
> impedances? Nevertheless, Terminator is explicitly prohibited from use as
> a Model_type with [Algorithmic Model].****
>
> ** **
>
> The parser (IBISCHK5, 5.1.2) correctly yields the following for such a
> combination:****
>
> ** **
>
> ERROR – Algorithmic Model is not allowed for model modelname which is of
> type Terminator.****
>
> ** **
>
> There’s a related issue that there’s no way to check whether I am
> combining a transmitter-only [Algorithmic Model] with an input or
> Terminator Model_type, but that’s a separate problem. ****
>
> ** **
>
> Is it time for a BUG and a BIRD?****
>
> ** **
>
> **- **MM****
>
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