[ibis-macro] Re: IBIS is very clear about Typ, Slow-Weak, and Fast-Strong in section 9.

  • From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
  • To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
  • Date: Mon, 10 Oct 2011 16:49:52 +0000

Walter,

Regarding: "This what is meant by "in accordance" with corner chosen
to do the simulations by the EDA tool." and: "So if you want to replace
the "in accordance" sentence with", I wonder what text you are
referring to, because I don't see the words "in accordance"
in the debated section.  I suspect you are talking about
this sentence:


"| Note that in the context of Algorithmic Model for type 'Corner', <slow
| value> and <fast value> align implicitly to slow and fast corners, ..."

I just want to be sure we are talking about the same thing...

Now, as to the topic itself, regarding: "Since IBIS only defines Typ,
Slow-Weak, and Fast-Strong,", while you are correct that min/max for
the I-V and V-t tables (including [Ramp]) can be interpreted as
"Slow-weak" and "Fast-strong", such interpretation for other
parameters, most notably C_comp, doesn't exist in the spec.  We
are not hung up on the interpretation of the I-V and V-t tables,
we are hung up on the interpretation of the complete model which
includes C_comp.  Based on the information in an IBIS model we
simply don't know what value of C_comp should be used with the
min or max I-V and V-t tables.

My proposal of extending the IBIS parameters to five values is
to provide a mechanism for the model maker to define what value
should be used for the fast and slow conditions.  These values
may or may not be the same as the min or max values.  I would
make them optional, and in the case they are not present, the
assumption would be that min=slow and max=fast.  For example,
if someone writes:

| variable  typ    min    max
C_comp      7.0pF  5.0pF  9.0pF

5.0pF should be used for a slow corner simulation and
9.0pF for a fast simulation.  But if someone writes:

| variable  typ    min    max    slow   fast
C_comp      7.0pF  5.0pF  9.0pF  8.9pF  5.1pF

Than a slow corner simulation should use 8.9pF and a
fast corner simulation should use 5.1pF.

This approach would not break old models, but would allow
new models to define the fast/slow corners for the analog
models as well.

This approach could be extended to all IBIS parameters which
are treated independently from the I-V and V-t curves.

Thanks,

Arpad
==============================================================

From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Walter Katz
Sent: Tuesday, October 04, 2011 7:25 PM
To: IBIS-ATM
Subject: [ibis-macro] IBIS is very clear about Typ, Slow-Weak, and Fast-Strong 
in section 9.

All,

Section 9 of IBIS clearly defines Typ, Slow-Weak and Fast-Strong

IBIS states:


It is permissible to use slow, weak components or models to derive the data for 
the "min" column, and to use fast, strong components or models to derive the 
data in the "max" columns under the corresponding voltage and temperature 
derating conditions for these columns.



And



The voltage and temperature keywords and optionally the process models control 
the conditions that define the "typ", "min", and "max" column entries for all 
I-V table keywords [Pulldown], [Pullup], [GND Clamp], and [POWER Clamp]; all 
[Ramp] subparameters dV/dt_r and dV/dt_f; and all waveform table keywords and 
subparameters [Rising Waveform], [Falling Waveform], V_fixture, V_fixture_min, 
and V_fixture_max.

The words "permissible" and "optionally" are  generally assumed by model makers 
and model users that at least for [Voltage Range], and [Temperature], IV 
Curves, VT Curves, and dV/dt all associate the Typ, Min, and Max columns with 
Typ, Slow-Weak and Fast-Strong.

An AMI parameter with Format Corner simply states that its value to be chosen 
by the EDA tool should correspond to the IBIS corner of the IBIS analog model 
when generating the Impulse Response of the channel. This what is meant by "in 
accordance" with corner chosen to do the simulations by the EDA tool.

Since IBIS only defines Typ, Slow-Weak, and Fast-Strong, then the three Format 
Corner values correspond to Typ, Slow-Weak, and Fast-Strong.

So if you want to replace the "in accordance" sentence with

The three values of an AMI Corner parameter value shall be chosen to correspond 
to the IBIS corner of the IBIS analog model when generating the Impulse 
Response of the channel.

Walter


Walter Katz
wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>
Phone 303.449-2308
Mobile 720.333-1107

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