RE: [IBIS] RE: [IBIS-Users] Query reg. USB1.1 IBIS model generation

From: Muranyi, Arpad <Arpad_Muranyi_at_.....>
Date: Tue Jan 22 2008 - 11:22:25 PST
Lynne,
 
I don't think Vivek was talking about IBIS1.1.  I thought
he was referring to USB1.1 as opposed to USB2...
 
Arpad
===========================================================

________________________________

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On
Behalf Of Lynne D. Green
Sent: Tuesday, January 22, 2008 11:17 AM
To: ibis-users@server.eda.org; ibis@server.eda.org
Subject: RE: [IBIS] RE: [IBIS-Users] Query reg. USB1.1 IBIS model
generation


Vivek,
 
You might want to check with your EDA vendor.  IBIS 1.1 is old, and not
compatible with later versions of IBIS (especially 3.2 and 4.x).
Consequently, support for some features might not function as expected.
 
Lynne
 
 
"IBIS training when you need it, where you need it."
 
Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@mindspring.com


________________________________

	From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf
Of Muranyi, Arpad
	Sent: Tuesday, January 22, 2008 10:11 AM
	To: ibis-users@eda.org; ibis@eda.org
	Subject: RE: [IBIS] RE: [IBIS-Users] Query reg. USB1.1 IBIS
model generation
	
	
	Vivek,
	 
	Generally, legacy IBIS is not able to describe buffers which
	have feedback.  You can, however, describe any behavior with
	the *-AMS extensions in IBIS.  On the other hand, if you are
	lucky, you may still be able to make a model using legacy
	IBIS features if you know exactly what your buffer does and
	you know how IBIS models work.  This may require some trial
	and error, and I am not in a position to guide you through
	this.
	 
	Regarding the 45 Ohm R_fixture question, you will get the best
	correlation when R_fixture equals the T-line impedance.  The
	model will still work well if the T-line has a different
	impedance, but the farther you go away the less accuracy you
	can expect.  Give it a try...
	 
	Arpad
	----------------------------------------------------------------

________________________________

	From: Vivek kumar Singh [mailto:Vivekkumar.Singh@arm.com] 
	Sent: Monday, January 21, 2008 11:27 PM
	To: Muranyi, Arpad; ibis-users@eda.org; ibis@eda.org
	Subject: RE: [IBIS] RE: [IBIS-Users] Query reg. USB1.1 IBIS
model generation
	
	

	Hi Arpad,

	     For both low and high speed usb, I generated IBIS models
with R_fixture of 50 Ohms. 

	 

	Mine is USB1.1.  I then did correlation with spice model. Full
speed was matching, but Low speed is not matching with spice.

	 

	2 queries I have :

	   1) In Low speed design, I have slew correcting feedback
capacitors. So, while generating IBIS should I take care of it
separately or IBIS will handle it? 

	   

	   2) For USB1.1, 45 Ohm R_fixture is used. So, while validating
should I use TLINE also of 45 Ohm? What changes should I make?

	 

	Regards,

	Vivek

	 

	
________________________________


	From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf
Of Muranyi, Arpad
	Sent: Monday, January 21, 2008 10:07 PM
	To: ibis-users@eda.org; ibis@eda.org
	Subject: [IBIS] RE: [IBIS-Users] Query reg. USB1.1 IBIS model
generation

	 

	Vivek,

	 

	R_fixture has nothing to do with the 1.5k or 15k resistors.

	Select a value for R_fixture that matches the transmission

	line impedance.  In the USB case it would be 45 Ohms (single

	ended) if my memory serves me right.

	 

	I would also suggest that you look at the IBIS Cookbook for

	help.  There are a lot of good ideas in there.

	 

	http://www.vhdl.org/pub/ibis/cookbook/cookbook-v4.pdf

	 

	Arpad

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

	 

	
________________________________


	From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org] On Behalf Of Vivek kumar Singh
	Sent: Sunday, January 20, 2008 10:34 PM
	To: ibis-users@server.eda.org; ibis@server.eda.org
	Cc: Vijaya kumar Vinukonda
	Subject: [IBIS-Users] Query reg. USB1.1 IBIS model generation

	Hi All,

	    I'm having problem with ibis model generation for USB1.1 . 

	I have following 3 queries :

	 

	since USB operates in Upstream and Downstream applications with
pullup and pulldown resistors 1.5k and 15k Ohm respectively. Will it
have any effect on choosing R_fixture value for IBIS VT data generation
????

	 

	What actually we take the value of R_fixture for USB1.1 ?

	 

	Can someone elaborate on setup for Ibis model generation for
USB1.1.

	 

	 

	Regards,

	Vivek

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Received on Tue Jan 22 11:23:05 2008

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