====================================================================== IBIS INTERCONNECT TASK GROUP http://www.ibis.org/interconnect_wip/ Mailing list: ibis-interconnect@freelists.org Archives at http://www.freelists.org/archive/ibis-interconn/ ====================================================================== Attendees from May 4 Meeting (* means attended at least using audio) ANSYS Curtis Clark* Cadence Design Systems Bradley Brim Cisco David Siadat Intel Corp. Michael Mirmak* Keysight Technologies Radek Biernacki*, Ming Yan Mentor Graphics Arpad Muranyi* Micron Technology Justin Butterfield*, Randy Wolff* SAE ITC Maureen Lemankiewicz, Logen Johnson Signal Integrity Software Walter Katz*, Mike LaBonte* Teraspeed Labs Bob Ross* University of Aveiro in Portugal Wael Dghais Michael Mirmak convened the meeting. No patents were declared. No minutes were available from the April 27 meeting for review. They will be sent out before the May 10 meeting. During opens, Walter Katz mentioned that, due to the IBIS Summit, he will be out next week and the following week, and therefore unable to attend meetings those weeks. Randy Wolff mentioned he would also be absent for the next meeting as well. Bob Ross suggested that the next meeting focus on the “tedious edits” needed to prepare the proposal for a vote. Michael noted that he has received no response from Brad Brim on the shortcut proposal. Bob re-raised the subject of handling of unused terminations. Radek Biernacki proposed that unstated terminations should be open- circuited; see page 9 of the current proposal for the relevant text. Bob replied that the default is in question; what should tool do if the termination is unstated. Touchstone and IBIS-ISS differ on this point. Bob’s objection is only in relation to the Touchstone exception (sentence: “If File_TS is present, then the EDA tools...”). Mike LaBonte suggested that the text is really giving the model-maker instructions, not saying what tool shall do. He proposed a phrase similar to “The model maker shall assume the EDA tool will connect terminals to terminations to prevent numerical instability.” This is similar to the SPICE assumption of GMIN 1/terraohm. Bob suggested an alternative: that any unused terminal shall be terminated by a connection determined by the EDA tool. Walter explained why this text would be used – imagine an IBIS-ISS 100-pin whole-package subcircuit. For this particular simulation, you only need to use two terminals. If there isn’t routing to every one of those pins, you would want to terminate many of them to 50 ohms to ground. If not, then you would terminate using a very large impedance to ground. Mike replied that the current SPICE documentation may include this. He accepted the AR to look up a representative example and provide it to the list. Bob responded that one could have the same model generating two different answers in simulation due to terminations. The issue is what the terminations are. If the terminal is undefined, you are presuming no connection if an external file is present. Therefore, you assume an open circuit. In some simulators, this is GMIN. The team agreed to change the specification by removing the sentence, “If this parameter is not defined and File_IBIS-ISS is present, then the EDA tool…” Michael accepted the AR to modify the text offline. Radek accepted the AR to review the text offline. Mike noted that no other major issues were found as a result of his review and edits to the current draft. Comments can be removed as we review future versions. The introductory non-specification paragraph should be its own introduction; the same change should be made with the text at the end of [Bus Label]. Michael accepted the AR to combine and move these. Bob noted that the word “field” is occasionally used instead of “entry”, “argument” or “column header”, particularly for [Pin Mapping] and Number of Pins. This should be corrected. Bob added that particular care is needed in integrating the document, with at least two reviews. Bob noted that at least one diagram is incorrect regarding Die Pads, as there are Pad Rails and Pad I/O terminals being used instead. Bob added that a minimal example was sent out; corrections to existing examples were shown. Bob’s fuller example is still pending. All examples should use File_IBIS-ISS or File_TS. He suggested that all example model names be cleaned up; shorter is preferred. Mike added that Number of Terminals is required, too. Walter reminded the team that Brad Brim’s shortcut discussion still pending. Otherwise, he proposed the team still submit the BIRD to the Open Forum in June (by June 30), imperfections and all. He volunteered to create a parser and convert existing package examples to new format, after the text is finalized. Bob raised objections to Interconnect Model Selector via e-mail. Michael will integrate Bob’s comments offline. Radek moved to adjourn. Mike seconded. The meeting adjourned