IBIS Macromodel Task Group Meeting date: 17 April 2018 Members (asterisk for those attending): ANSYS: Dan Dvorscak Curtis Clark Cadence Design Systems: Ambrish Varma Brad Brim Kumar Keshavan Ken Willis eASIC: David Banas GlobalFoundries: Steve Parker IBM Luis Armenta Trevor Timpane Intel: * Michael Mirmak Keysight Technologies: Fangyi Rao * Radek Biernacki Ming Yan Mentor, A Siemens Business: John Angulo * Arpad Muranyi Micron Technology: * Randy Wolff * Justin Butterfield SiSoft: * Walter Katz Todd Westerhoff * Mike LaBonte SPISim: Wei-hsing Huang Synopsys: Rita Horner Kevin Li Teraspeed Consulting Group: Scott McMorrow Teraspeed Labs: * Bob Ross The meeting was led by Arpad Muranyi. Mike LaBonte took the minutes. -------------------------------------------------------------------------------- Opens: - None. ------------- Review of ARs: - Arpad to contact Fangyi about whether he wants to be listed as an author on the new BIRD to supersede BIRD158.7. - Done. No reply yet. Fangyi may be away. -------------------------- Call for patent disclosure: - None. ------------------------- Review of Meeting Minutes: - Arpad: Does anyone have any comments or corrections? [none] - Mike L.: Motion to approve the minutes. - Radek: Second. - Arpad: Anyone opposed? [none] ------------- New Discussion: BIRD189 and BIRD158 related issues: - Arpad showed a warning paragraph emailed by Radek. - Radek: It combines and rephrases the two "Important" paragraphs. - Arpad showed the two paragraphs. - Bob: We have not discussed the third "important" message yet. - Arpad: We did, at least a week ago. We were done with that. - Walter: The last line should have "be" between "may" and "less". - Radek: It should not have "less". - Arpad changed that to "may be inaccurate". - Bob: The results could be inaccurate regardless of the subcircuit content. - Arpad: This paragraph says what the simulator should do. - Radek: It has Michael's language about node 0 being treated as an additional terminal. - Michael: I came up with something different. - Arpad showed Radek's original text. - Arpad: We should say we highly discourage model makers from using node 0 because it may affect accuracy. - Walter: The reason is that not all currents might go to reference nodes. - Radek: This is the return path problem. - The "shall be treated" phrase can be replaced. - It is the same if A_gnd is used. - Arpad: A_gnd is given in the [Interconnect Model]. Node 0 is hidden. - Walter: Brad says they don't support node 0 in subcircuits. Not sure how they do that. - Radek: Node 0 and A_gnd give the same functionality. - Michael M: A_gnd is not in IBIS-ISS. Do we need to mention A_gnd as existing inside the subcircuit. - Radek: We allow A_gnd for instantiation. - Arpad: A_gnd is different from having it inside the subcircuit. You have more control with A_gnd. - Walter: We have to assume the person wrapping the models also creates them. - Radek: Bring those nodes out can be tedious and error prone. - Bob: ISS supports node 0 as global. It is not declared as a terminal. - The user doesn't know if it's used, but an EDA tool could find out. - Radek: We are trying to write a warning here. - The EDA tool will know if node 0 is used. - Arpad: Who are we writing the warning for? The maker, tool, or user? - Michael M: All three. Model makers should be reminded to watch out. - Sometimes users have to fix the models themselves. - Bob: What should the checker say? - Walter: This will be in IBIS, not checked. - Bob: Someone should write a node 0 detection script. - Michael M: It could be a differentiator for an EDA tool. - Arpad: If all three should be warned, this needs to be worded differently. - Walter cited his suggested wording. - Walter: We are talking about uV to mV of effects. - Radek: We should not try to quantify the problem. - Michael M: We could keep the current sentence and add Walter's message. - Walter: We should not "highly discourage". We should say what it will do. - Arpad showed text from Walter. - Walter described current loop issues. - Bob: What's wrong with doing this in ISS? - Walter: Nothing. People do it today, even in power aware simulations. - Most of the voltage drop comes from the buffer itself. - Arpad showed a modified warning message. - Arpad: Is this acceptable. - Michael M: That looks good. - Radek: It does not mention A_gnd. - Arpad added an A_gnd clause. - Radek: It should not have "ground". - Walter: That was because ground pins are used as references for measurements. - Arpad: We could say it does not account for all current going through the component's pins. - Walter: IBIS is a databook component spec. Some of those pins are ground. - I had a sentence about the historical use of "ground". - Arpad: If done right, all current goes through the pins. - This is an additional path. - We should say that some current would not go to the pins. - Walter: We should define what ground is. - Bob: We do not agree on that. It would not support ECL/PECL. - Michael M: It can mention pins, but it does not have to be exhaustive. - Radek: What we have here is sufficient. - Bob: In simulation node 0 is universal as a ground. - Michael M: If we expect all current to go through the pins, the math will not come out correctly. - Arpad removed "ground" and the "power aware" clause. - We agreed on the language. - Arpad: Should this be "warning" or "important"? - We agreed to make it a note. AR: Arpad to send edited node 0 note text to list. - Michael M: If we still agree on this we can resolve the remaining BIRD 189 issue comments in the next meeting. - Michael M.: Motion to adjourn. - Mike L.: Second. - Arpad: Thank you all for joining. ------------- Next meeting: 24 April 2018 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives