RE: [IBIS-Users] IBIS Model Usage:

Hi Muniswara,

I am responsible for IBIS model construction at my employer and can relate what we do. Customers often have a "check box" based development flow where modelling is one of those steps. So IBIS models are clearly vital for SoC vendors these days. Simplicity is key. We incorporate everything into one IBIS model for an SoC to simplifiy internal review and release control.

In addition to Slow/Typ/Fast corner cases, there are many types of IOs as well. The IO types include general purpose with drive control settings between 2mA to 10mA, LVDS IO, and DDR/2/3 with multiple drive strengths and ODT settings. One of the tricks I use is to have both a pin-based model, and "plain" IBIS buffer types listed (in the model they are behind pins "Z1,Z2,Z3..." with RLC values of zero). This way the customer can see the different types of models listed as "Base_LVDS, Base_GPIO, etc" at the top of the file, or they can proceed to use the alphanumeric pin list that incorporates extracted RLC values.

I recommend downloading an IBIS file from a major company such as Micron. Their philosophy seems to be including multiple part numbers of the same DDR class as one file.

Regards
-Graham

________________________________
From: owner-ibis-users@eda.org [owner-ibis-users@eda.org] On Behalf Of Timothy Coyle [tim.coyle@siconsultant.com]
Sent: Tuesday, May 10, 2011 11:04 AM
To: 'Muniswara Reddy Vorugu'; 'ibis-users'
Subject: RE: [IBIS-Users] IBIS Model Usage:

Hi Muniswara,
The main advantage of providing one IBIS file for your users is ease of use. I think for most designs you can pretty much merge everything into one IBIS file. It might get more complicated if you are using advanced keywords etc. but with Model Selector and other IBIS spec support you can almost always get it all in one file.

Arpad mentioned some good points about process corner settings and that's really something you will have to define within your group and document for end users.

And to give you a specific usage case think about when your end user needs to take the IBIS file and assign it to a CAD layout tool to run simulations. They will only allow one IBIS file to be used so your end user has to manually put your three files into one. Then they also have to probably modify or create the package pin section which can be time consuming.

Best,

Tim

From: owner-ibis-users@eda.org<mailto:owner-ibis-users@eda.org> [mailto:owner-ibis-users@eda.org]<mailto:[mailto:owner-ibis-users@eda.org]> On Behalf Of Muniswara Reddy Vorugu
Sent: Tuesday, May 10, 2011 1:21 AM
To: 'ibis-users'
Subject: [IBIS-Users] IBIS Model Usage:

Hi,
For better delivery of IBIS model, we want to know better ways to get usablility and manage our deliverables.
To make this balance, I want to understand the following:

1: What are the advantages of min/typ/max corners merged in single file, over 3 files with one corner per file?
What is the difficulty for running Min/Typ/Max corners analysis.
Are there any Fundamental analysis limitations?

Regards,
Muniswara

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