[IBIS] RE: [IBIS-Users] issue in VT extraction

From: Muranyi, Arpad <arpad.muranyi_at_.....>
Date: Tue Feb 07 2006 - 09:31:25 PST
Kiran,
 
I understand that you can't send us your circuit files, don't
worry about that...
 
It sounds like your SPICE model may have flip/flop-s in it,
and the first transition gives you an incorrect voltage
because SPICE doesn't initialize all nodes correctly, and
consequently there may be some internal contentions inside
the circuit.  After the first transition the f/f-s are in
a "known state" and from there on your waveforms are correct.
 
This may only show up on one side of the differential output
because they are in a complementary state, and by chance it
may be possible that the f/f for one output happened to 
start in the correct state, but the f/f for the other output
didn't (since it had to be in the opposite state).
 
As Lynne wrote, there is no requirement that you take the
first transition of this simulation for the IBIS model
data.  To the contrary, for these and similar reasons we
usually prefer to take the data from later transitions
when the buffer is more in the "steady state" conditions.
 
I hope this will help you in your work.
 
Arpad
------------------------------------------------------------
 


________________________________

From: seshadri.kirankumar@wipro.com [mailto:seshadri.kirankumar@wipro.com] 
Sent: Tuesday, February 07, 2006 4:23 AM
To: Muranyi, Arpad; ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS-Users] issue in VT extraction



Arpad ,  

 

       I am not doing simulation on IBIS file but in the procedure to generate IBIS model of VT data i.e Rising and Falling connecting to VSS that means  the plot which you saw was spice3 simulation result done on the spice netlist using 2 decks one for Rising and one for Falling. As I don't have permissions to send this decks and inputs for generation of IBIS I could not send across.

 

 Hope this clear your point spice3 does not have feature to simulate IBIS model.  

 

Best Regards

Kiran Kumar

 

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad
Sent: Monday, February 06, 2006 10:00 PM
To: ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS-Users] issue in VT extraction

 

Kiran,

 

I am not sure whether you answered my question

correctly.  I was wondering what simulator did

you use to simulate the IBIS model, not what

simulator you used to generate the Vt data

for the IBIS model.

 

Does spice3 have an IBIS buffer element?

 

Arpad

===============================================

 

________________________________

From: seshadri.kirankumar@wipro.com [mailto:seshadri.kirankumar@wipro.com] 
Sent: Thursday, February 02, 2006 8:21 PM
To: Muranyi, Arpad; ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS-Users] issue in VT extraction

Arpad,

 

         This data for plot is generated using spice3 

 

Best Regards

Kiran Kumar

 

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad
Sent: Thursday, February 02, 2006 10:06 PM
To: ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS-Users] issue in VT extraction

 

Kiran,

 

Which simulator did you use when

you made this waveform?

 

Arpad

================================

 

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of seshadri.kirankumar@wipro.com
Sent: Thursday, February 02, 2006 3:19 AM
To: ibis-users@eda.org; ibis@eda.org
Subject: [IBIS-Users] issue in VT extraction

Hi IBIS Experts,

 

    I have an query  in IBIS modeling about extracting VT data, 

I am generating model for one buffer which is having its output swing from +0.21V to -0.21V, But as you see in the Plot for 

Rising (if the i/p pulse is Rising ) then it is giving proper switching (Red coloured) 

But in Falling (if the i/p pulse is falling) then for  1 st pulse it is not going down and reaching to -0.21V even I tried giving very low frequency i/p signal(Green coloured).

 

Here my doubt is why IBIS takes first 1/4 th of Pulseperiod of i/p signal, is there any reason in that? 

 

 If there is no any constraint on this  as I am seeing the good performance in second pulse onwards I can do  a X-axis shift (Time shift) of the second Falling Pulse.

 

I wanted this clarification because I am not aware of internal architecture which causing this problem in the netlist(input) which I am using for generation.

 

Thanks in Advance

 

Best Regards

Kiran Kumar

 


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WARNING: Computer viruses can be transmitted via email. The recipient should check this email and any attachments for the presence of viruses. The company accepts no liability for any damage caused by any virus transmitted by this email.

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Received on Tue Feb 7 09:32:03 2006

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