IBIS Macromodel Task Group Meeting date: 01 May 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: - Arpad noted that Mike LaBonte was taking minutes. He also suggested we might discuss Bob's recent email. Bob said that email was sent to the interconnect group, and should be discussed the next day. ------------- Review of ARs: - Michael M. to produce BIRD189.6 draft18 version 9 and email it to the list. - Done (should be BIRD189.5 draft18 version 9). -------------------------- Call for patent disclosure: - None. ------------------------- Review of Meeting Minutes: - Arpad: Does anyone have any comments or corrections? [none] - Bob noted that the AR should have stated "BIRD189.5 draft18 version 9". - Mike L.: Motion to approve the minutes with correction as noted. - Bob: Second. - Arpad: Anyone opposed? [none] ------------- New Discussion: BIRD189 related issues: - Discussion: Michael M. reaffirmed that Bob's rail proposal would be discussed the next day. BIRD158 related issues: - Arpad showed a version of BIRD158.7 with all recently agreed updates made. - Discussion: Arpad noted that he had an AR to check with Fangyi and keep all original authors listed. With the informational messages recently removed from BIRD189, we should refrain from discussing the topic of channel referencing in BIRD158. The text explaining the Rx figure has been updated. Arpad said it should be ready to submit to the Open Forum. Radek noted that the channel figure had been removed. He said that he had already pointed it out that with A_gnd being now the global ground it is critical to state that the channel needs to be referenced to A_gnd as well. Otherwise there would be a direct connection between Tx and Rx bypassing the channel and that is incorrect. For that reason the removed figure should be reinstated. Arpad said that would be just educational material. Radek felt IBIS should describe what is allowed. Arpad said in SPICE we get an error is there is no path to node 0, asking if it our job to prevent such mistakes, noting that we had discussed preferring not to do that. Michael M. asked if there could be a cookbook. Arpad noted that Walter had written an email about IEEE P370, giving an example of a simple statement about connections. Radek said that seemed like a digression. Arpad said that polarities could be reversed, but that would be an unconventional use. He asked if we really needed to say anything about it in the spec. Michael M. asked if such a statement would be parsable. Radek said yes, and the package should be referenced to A_gnd at the pin interface. Arpad said the packages could be referenced in several different ways, and we might need to show that. The deleted drawing shows only a subset of the possibilities. Radek disagreed, saying that at the pin interface there should be just two I/O terminals and A_gnd. Arpad said we would not want to imply that just one way is the only way to do it. Radek disagreed, saying that having two I/O terminals and A_gnd is the only way. Furthermore, package modeling allows other terminals to be present at the pin interface and. For example, with no guidance it might not be clear how to connect a 6-port model to a 4-port channel. Randy suggested that that would be white paper material, and it was not what our specification is for. He was prepared to motion to move forward. Bob noted that the BIRD158 format was for AMI usage only, and that delineating reference connections was irrelevant in that case. Mike L. asked if IBIS wasn't clear on how to connect AMI buffers before we introduced Touchstone analog models. Arpad said we had issues in that area since the beginnings of the spec with figures package capacitance and C_comp connected to “GND”. Those problems were masked by not doing power delivery analysis in those days as we do them today. Radek said now that we have A_gnd, new questions are raised about how to connect, and that this topic should not be excluded. He said we can not wait for another cookbook. Michael M. suggested we could have articles in industry magazines. Arpad agreed with that suggestion. He asked what problems would exist if we did not have the channel figure. No one raised any problems. Bob said the BIRD suggests a common reference throughout, and that node 0 is acceptable for that. Michael M. suggested one or maybe a couple drawings would be needed, and that it would take too long to add those, given our expected IBIS 7.0 schedule. We could instead have articles, a cookbook, and maybe a panel discussion. Arpad said we would need to work carefully on the verbiage, noting that packages can also be described with IBIS-ISS. Radek said without guidance someone could allow the channel to be floating, for example. Arpad said he did not want to hold up IBIS 7.0. - Randy moved to submit the BIRD as is to the Open Forum. - Michael M. seconded. - Arpad: anyone opposed? - Roll call vote: Intel: Yes Keysight: No Mentor: Yes Micron: Yes SiSoft: Yes Teraspeed Labs: Yes - With 5 Yes and 1 No, the motion passed. AR: Arpad to submit BIRD158_new to Open Forum Agenda discussion: - Arpad showed the list of potential agenda topics. He noted that Walter was not present, and therefore we should not discuss his drawing. Arpad asked for suggestions on what to discuss next week. Michael M. asked if complex C_comp would be part of IBIS 7.0. Randy said it would be after IBIS 7.0. Arpad asked if it was still needed. Randy said yes, because it is a buffer level feature. Bob agreed. Mike L. asked if EMD would address this. Arpad asked if we discuss EMD in this group. Randy said this was a buffer level issue. Michael M. said it was important. Mike L. said the FEC topic had been brought up at the DesignCon summit, and that it was really about how to let models provide post-simulation analysis. Radek said the third item was important, using Terminator models for AMI Rx. Arpad said the fourth item about thresholds was described as a model issue, not a specification issue. Michael M. asked if a buffer can be used in several contexts, how do you communicate the context. Arpad suggested we could point to other specifications. Mike L. suggested that this seemed related to FEC and other needs for post-simulation analysis. Bob asked if the issue was tied to IEEE, JEDEC specifications, etc. Arpad said it was more about things the model should not violate, not the operation of the model itself. For example, the TTL high and low limits. That was not model behavior. Mike L. noted that IBIS already contain information that is not about model behavior. Bob said it would be referring to something that can be measured, such as an eye diagram. Arpad noted that that kind of information helps EDA tools automate the process. Bob asked if a single buffer could be used for multiple industry specifications. Arpad asked if removing single ended characterization requirements for differential buffers was important. Michael M. said Vmeas, Cref, etc. should not be required for diff pairs, because they are not defined for those buffers. Mike L. said that would be a rule relaxation, and should be no problem. Bob said that that was a mistake made in AMI. Arpad said the issue was about diff pairs, not AMI, noting that in IBIS, diff pairs are really a pair of single ended buffers. Michael M. said the guidance for how to use power aware keywords such as [ISSO] with AMI was not clear. He suggested it should be defined in the specification if and how [ISSO] etc. affect AMI buffers. Arpad said that could become a big discussion topic. - Michael M.: Motion to adjourn. - Mike L.: Second. - Arpad: Thank you all for joining. ------------- Next meeting: 08 May 2018 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives