[ibis-macro] Re: Jitter BIRD issues, and Buffer Tstonefile Issues

Fangyi,

We had extensive discussions on this topic earlier this
year when Scott expressed his concerns about the S-parameter
based analog buffer models described in the various versions
of the "analog modeling BIRD-s".

The summary of that discussion was captured in a PPT file
based on the comments and discussions of the participants
of the ATM task group.  The decisions we made are noted in
red letters on the last slide.  I wrote this presentation
to document the outcome of our discussion and so that at
the time when we write/edit the analog BIRD(s), we would
have our decisions ready to go without having to rehash the
same discussions again.  The intent is to put the definitions
and statements in this presentation into the IBIS specification
in the area where the analog models using S-parameter models
are described.

Please refer to this document with your questions and
discussions on this topic.  I do not want to go through
the same conversation again... (it was long, complicated,
and at times somewhat painful).

Thanks,

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

From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Walter Katz
Sent: Thursday, December 01, 2011 9:05 PM
To: fangyi_rao@xxxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Jitter BIRD issues, and Buffer Tstonefile Issues

Fangyi,

Why not let the EDA tool decide how to terminate it, based on the simulator 
being used?

Walter

From: fangyi_rao@xxxxxxxxxxx<mailto:fangyi_rao@xxxxxxxxxxx> 
[mailto:fangyi_rao@xxxxxxxxxxx]<mailto:[mailto:fangyi_rao@xxxxxxxxxxx]>
Sent: Thursday, December 01, 2011 9:04 PM
To: wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>; 
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: [ibis-macro] Jitter BIRD issues, and Buffer Tstonefile Issues

Hi, Walter;

Regarding touchstone file, the Rx E element is equivalent to terminating the Rx 
S-parameter block with open. Since some internal tools used by IC vendors don't 
assume the same termination condition, it's better to allow model developers to 
specify termination to avoid confusion when correlating with internal tools.

Regards,
Fangyi

From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> 
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]>
 On Behalf Of Walter Katz
Sent: Tuesday, November 29, 2011 2:31 PM
To: IBIS-ATM
Subject: [ibis-macro] Jitter BIRD issues, and Buffer Tstonefile Issues

All,

The remaining major issue is the handling of Rx_Rj, Rx_DCD, and Rx_Sj.

1.       It has been requested that Rx_Dj be added.

2.       First a discussion on how the Rx clock is handled in the following two 
cases

a.       Time Domain

                                                              i.      Rx 
AMI_GetWave returns clock ticks in *clock_times.

b.      Statistical

                                                              i.      Rx 
AMI_GetWave does not return clock ticks in *clock_times.

                                                            ii.      Using Rx 
AMI_Init

3.       The current BIRD 123 states that Rx_Rj, Rx_DCD, and Rx_Sj shall be 
applied to both Time Domain and Statistical methods.

a.       In Time Domain, Rx_Rj, Rx_DCD, and Rx_Sj can be applied to times in 
clock_times, statistically to the clock_times PDF, or statistically to the 
persistent eye.

b.      In Statistical, Rx_Rj, Rx_DCD, and Rx_Sj are combined statistically 
along with Rx_Clock_PDF, Rx_Clock_Recovery_Rj, Rx_Clock_Recovery_DCD, and 
Rx_Clock_Recovery_Sj.

4.       It has been suggested that Rx_Rj, Rx_DCD, and Rx_Sj shall apply to 
just Time Domain.

a.       In Time Domain, Rx_Rj, Rx_DCD, and Rx_Sj can be applied to times in 
clock_times, statistically to the clock_times PDF, or statistically to the 
persistent eye.

b.      In Statistical, only Rx_Clock_PDF, Rx_Clock_Recovery_Rj, 
Rx_Clock_Recovery_DCD, and Rx_Clock_Recovery_Sj are applied.

Regarding Tstonefile.

1.       Fangyi and I agreed the there is no requirement that S12=S21, and that 
S21 can be small or zero.

2.       Fangyi and I agreed that the input to the Tx, and the output of the Rx 
S element be isolated with a unit gain amplifier (E element) as in the 
following example of a Tx Tstonefile wrapped in an ISS subckt:

a.  .subckt Intrinsic_Tstonefile_Tx DieP PadP DieN PadN file='NA'

b.  * Port order of Touchstone file is DieP PadP DieN PadN

c.  E_H EDieP 0 VCVS DieP 0 1.

d.  E_L EdieM 0 VCVS DieN 0 1.

e.  S1 EDieP PadP EDieN PadN 0 mname=A

f.  .model A TSTONEFILE=file

g.  .ends Intrinsic_Tstonefile_Tx

3.       There are now three proposals to implement Tstonefile in .ibs and/or 
.ami files.

a.       BIRD 120 proposes the following example, where  (Voh-Vol) = Peak to 
Peak voltage swing:

                                                                                
      i.      (Tstonefile (List "xwc.s4p" "wc.s4p" "nc.s4p" "bc.s4p" "xwc.s4p")

                                                                                
    ii.      (Usage Info) (Type String)

                                                                                
  iii.      (Description "Extreme Worst, Worst, Nominal, Best, Extreme Best"))

                                                                                
   iv.      (Vol  (Value 0.) (Usage Info)(Type Float))

                                                                                
     v.      (Voh (Range 1 .3 1.2) (Usage Info)(Type Float))

b.      There are a number of BIRDs submitted by Arpad and Ambrish. I have 
requested that the above example be implemented using the syntax proposed in 
these alternative BIRDs.

Walter


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

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