[ibis-macro] Re: Terminator Model_type and *input* Algorithmic Models?
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: <mike@xxxxxxxxxxx>, "'Bob Ross'" <bob@xxxxxxxxxxxxx>
- Date: Sat, 5 Jan 2013 13:36:24 -0500 (EST)
All,
More importantly, what is the advantage of using Terminator instead of
Input? Does Terminator (instead of Input) offer any advantages?
Walter
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike LaBonte
Sent: Saturday, January 05, 2013 12:27 PM
To: Bob Ross
Cc: Mirmak, Michael; IBIS-ATM
Subject: [ibis-macro] Re: Terminator Model_type and *input* Algorithmic
Models?
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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