Thanks Arpad I would study the use of [Alternate Package Models] and try constructing a sample to make sure I understand it completely. On use of s-parameters, I would discuss with the team in Cadence to see what they think about it and that whether there is an easy way to represent stuff. rgds ..kukal ________________________________ From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Thursday, January 13, 2011 11:04 PM To: IBIS-ATM Subject: [ibis-macro] Re: BIRD-125: ISS as package-model Kukal, Your statement that "the BIRD requires the user to always specify one sub-circuit for the whole package" is incorrect. The [Pin Numbers] keyword in the package model does NOT have to have a full listing of all the pins listed in the [Pin] keyword of the .ibs file. So you may have a 10000 pin device with a 6 pin package model (which describes three differential SERDES channels, for example). You may wonder, how would you then be able to describe several different subsets of the 10000 pin device if there is only one [Package Model] keyword in an .ibs file. This is when the [Alternate Package Models] keyword can be used. You can write a bunch of package models using the [Define Package Model] keyword, each of which can cover a different section of the full device, or give alternate versions for the same section, and when you simulate certain pins of the fill device, you would just select the corresponding package model from the [Alternate Package Models] keyword. Regarding the direct referencing of the S-parameter models, I think it is not a bad idea, but it has its own complications in the area of port ordering. If we invented such a direct reference to S-parameters, we would also need to make provisions for defining the port ordering. If you have ideas on how to do this, feel free to write a BIRD... I just like the ISS subcircuit approach better because there is more flexibility in the ISS subcircuit. A direct instantiation of the S-parameter may be somewhat simpler, but is only a subset of what ISS can do. Thanks, Arpad ================================================================================= From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Taranjit Kukal Sent: Thursday, January 13, 2011 1:26 AM To: IBIS-ATM Subject: [ibis-macro] BIRD-125: ISS as package-model Hi Arpad, The BIRD surely bridges a gap that was very important as almost every package needs to be an s-parameter model at MGH. However, it seems that the BIRD requires the user to always specify one sub-circuit for the whole package. So, if the package had 8, 16, or 100 pins then the user needs to provide a 16, 32, or 200 terminal subckt, respectively. We always get package models as models for single pins or diff-pin(s). I think we should extend the BIRD to include subcircuits per pin (and per-diff-pin) and may be cover cases where several smaller sub circuits can be assigned to subsets of the package pins. Another minor thing is that we are forcing the user to wrap s-parameter files into ISS - Not sure if the syntax should allow direct s-parameter instantiation. This is a surely not a big issue. rgds ..kukal Taranjit Kukal | Product Engineering Architect P: 91 120 3984000 www.cadence.com<http://www.cadence.com/>