[ibis-macro] Re: Some final questions on BIRD 123.

  • From: "Walter Katz" <wkatz@xxxxxxxxxx>
  • To: "'David Banas'" <DBanas@xxxxxxxxxx>, "'James Zhou'" <james.zhou@xxxxxxxxxx>
  • Date: Tue, 06 Dec 2011 17:40:14 -0500 (EST)



It was specifically requested by the EDA vendors that the EDA tool only
use the results of these Out parameters from Init, and specifically not
from GetWave. It is also an outstanding issue whether these should be
allowed as Out at all, and that we allow Info only. We have not seen any
request (or need) for them to be Out parameters, so I do not object if
they are Info only. The only reason I allowed Out was because Tx_DCD (in
IBIS 5.0) was allowed to be Out, and I was consistent with that.


The only parameter that must be allowed to be Out is Rx_Noise, and in this
case it must be allowed as an Out from GetWave. It turns out that the
amount of Rx_Noise that needs to be applied by the EDA tool is a function
of the Gain inside of the AGC in the Rx model. Since it is an "AGC", the
Rx GetWave can (and does) change the Gain which changes Rx_Noise which
needs to be accounted for in the EDA tool.




From: David Banas [mailto:DBanas@xxxxxxxxxx] 
Sent: Tuesday, December 06, 2011 5:28 PM
To: 'Walter Katz'; 'James Zhou'
Subject: Some final questions on BIRD 123.


Hi Walter,


I think I'm just about there. Just a couple of questions:


1.       Referring to this excerpt from the most recent version of the
BIRD (123.3_Draft1):



The EDA Tool/Simulator shall use the values of these Jitter and Noise
parameters directly if they are Usage Info. If they are Usage Out, then
the EDA Tool/Simulator shall use their values generated by AMI_Init. The
model's AMI_GetWave function may return different values for these
parameters than the values returned by AMI_Init; the EDA Tool/Simulator
may report the values of such parameters to the user, but the EDA
Tool/Simulator may not change any inputs to AMI models or change other
result of the simulation based on the values returned for the parameters
in this BIRD by AMI_GetWave. 


a.       Why is there a necessary difference in EDA tool behavior,
depending upon whether the parameters are of type Info or Out?

b.      If Init and GetWave can return different values for these
parameters, then why do we need 2 sets (i.e. - Rx_Sj and Rx_CDR_Sj)? It
seems like we ought to be able to have just one parameter, Rx_Sj, and let
Init return one value for it, while GetWave returns another, depending
upon how sophisticated its CDR modeling is.

c.       Referring to the last phrase, above, "or change other result of
the simulation based on the values returned for the parameters in this
BIRD by AMI_GetWave.": broadly interpreted, couldn't this phrase preclude
an EDA tool from applying the post-processing necessary for accurate BER
estimation? What is the purpose of this phrase?







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