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. 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