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

  • From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
  • To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
  • Date: Wed, 7 Dec 2011 05:32:40 +0000

Radek,

I don't know if you saw my previous message, so I
am going to repeat myself.  Way back in January,
we had extensive discussions on this topic lead
by Scott McMorrow, and we decided a few things
which were summarized in the following presentation:

http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20110125/arpadmuranyi/Analog%20Models%20for%20IBIS-AMI/IBIS_ATM_2011_01_25.pdf

Please review these slides and let me know if you
have any comments or questions about them.  My
understanding was that these decisions will be used
to formulate the words for the analog modeling
section of the IBIS specification whichever BIRD
will make it into the specification at the end.

Thanks,

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



From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of radek_biernacki@xxxxxxxxxxx
Sent: Tuesday, December 06, 2011 1:36 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Jitter BIRD issues, and Buffer Tstonefile Issues

Hi Walter,

I believe I mentioned that several times at the time of the extended 
discussions on this topic: there is absolutely no need for any unity-gain 
amplifier for both the TX and the RX. In general, defining the source impedance 
(for TX), and load impedance (for RX) could be left to the user - the 
S-parameters do not carry that information. Alternatively, they can be set in 
the specification. One possible (and in fact preferable) setting is the zero 
source impedance for TX (ideal voltage source) and an infinite load (open 
circuit) for the RX. The latter can be spelled out explicitly in the spec, and 
any addition of unity-gain amplifies results in exactly the same excitation and 
load conditions - thus they are completely redundant.

I believe, the issue of ignoring of S12 or insisting on any specific value was 
also discussed long time ago, and it was dismissed.

Radek


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: Friday, December 02, 2011 9:33 AM
To: RAO,FANGYI (A-USA,ex1); 
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: Jitter BIRD issues, and Buffer Tstonefile Issues

Fangyi,

The Rx Touchstone file includes the Rx termination! S21 is the signal 
propagated to the AMI algorithmic model, S11 is the signal reflected back to 
the channel. S12 is ignored by the EDA tool. One way to accommodate this in 
some SPICE simulators is to put a Unit Gain Amplifier (E element) between the 
output of the s parameter element and the SPICE "probe" at the output of the  
Touchstone file. (I am assuming that port 1 is at the pad of the die, and port 
2 is at the input to the algorithmic block of the Rx.

Does this explanation clearly define the derivation method that the model 
developer uses to create the Tstonefile, and the method the EDA tool uses to 
generate the Impulse Response of the channel when a Tstonefile is used by 
either the Tx and/or Rx?

Walter

From: fangyi_rao@xxxxxxxxxxx<mailto:fangyi_rao@xxxxxxxxxxx> 
[mailto:fangyi_rao@xxxxxxxxxxx]<mailto:[mailto:fangyi_rao@xxxxxxxxxxx]>
Sent: Friday, December 02, 2011 11:50 AM
To: wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>; 
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: [ibis-macro] Jitter BIRD issues, and Buffer Tstonefile Issues

Walter;

Termination is part of the Rx circuit. Only IC vendor knows it. EDA tool 
doesn't. If the tool arbitrarily terminates S-parameter block, the circuit is 
altered and you get different reflection back to Rx and channel. The ISS BIRD 
(116) allows the flexibility for model developers to define any termination 
they want because S-parameter block is just one of the circuit components in 
the analog model.

Fangyi

From: Walter Katz [mailto:wkatz@xxxxxxxxxx]<mailto:[mailto:wkatz@xxxxxxxxxx]>
Sent: Thursday, December 01, 2011 7:05 PM
To: RAO,FANGYI (A-USA,ex1); 
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: [ibis-macro] 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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