IBIS Macromodel Task Group Meeting date: 17 May 2022 Members (asterisk for those attending): Achronix Semiconductor: Hansel Dsilva Amazon: John Yan ANSYS: * Curtis Clark * Wei-hsing Huang Cadence Design Systems: * Ambrish Varma Jared James Google: Zhiping Yang Intel: Michael Mirmak Kinger Cai Alaeddin Aydiner Keysight Technologies: * Fangyi Rao Majid Ahadi Dolatsara Ming Yan Radek Biernacki Rui Yang Luminous Computing David Banas Marvell Steve Parker Mathworks (SiSoft): * Walter Katz Mike LaBonte Micron Technology: * Randy Wolff * Justin Butterfield Missouri S&T Chulsoon Hwang SAE ITC Michael McNair Siemens EDA (Mentor): * Arpad Muranyi Teraspeed Labs: * Bob Ross Zuken USA: * Lance Wang The meeting was led by Arpad Muranyi. Curtis Clark took the minutes. -------------------------------------------------------------------------------- Opens: - None. ------------- Review of ARs: - Arpad to send BIRD213.1 draft 24 to the ATM list. - Done. -------------------------- Call for patent disclosure: - None. ------------------------- Review of Meeting Minutes: Arpad asked for any comments or corrections to the minutes of the May 10th meeting. Ambrish moved to approve the minutes. Randy seconded the motion. There were no objections. ------------- New Discussion: PAMn BIRD 213.1 draft 24: The group resumed discussion of the PAM_Offsets Usage Rules. Fangyi noted that he had replied to Arpad's draft 24 email and provided a table summarizing the rules for statistical flow for the various combinations of parameter values. One correction to the table was noted: Rx_Decision_Time overrides Rx_Clock_Recovery_Mean (per the IBIS 7.1 Usage Rules for Rx_Decision_Time). So, if Rx_Decision_Time is specified for NRZ it is not added to Rx_Clock_Recovery_Mean (it replaces it). Walter referred to the last two sentences of PAM_Offsets Usage Rules (draft 24): Note: When Modulation_Levels is defined and is not equal to 2, Rx_Clock_Recovery_Mean is ignored. The offset described by Rx_Clock_Recovery_Mean should be included in PAM_Offsets. and said the phrase "should be included" was confusing. Walter suggested replacing the last paragraph with an enumerated list of the various combinations of Modulation_Levels value and Rx_Decision_Time's presence or absence. Walter took an AR to draft the enumerated list and proposed changes to the BIRD. Randy noted that page 213 of IBIS 7.1 contained an example of formatting for such an enumerated list. Ambrish asked whether this information should be repeated in the Rx_Decision_Time Usage Rules as well. Walter noted that PAM_Offsets is an output for statistical (AMI_Init) and time domain (AMI_GetWave). He asked what a model should do if it only wants to use it in time domain. Fangyi and Curtis said the model could returns zero(s) from AMI_Init. In an earlier email, Arpad had noted an additional section on page 280 that might need changes. At the end of the PAM4_Mapping parameter's Other Notes section is a two-item list headlined with the sentence: There are two reasons why a mapping is required. Arpad said this sentence is no longer true, since we don't require or provide a mapping with the new Modulation_Levels approach. Walter suggested simply replacing the word "mapping" with "PAM4_Mapping". Curtis suggested we also change "is required" to "is used." The group settled on: There are two reasons why PAM4_Mapping might be used. Ambrish then asked whether we need this sentence at all. Do we have to explain the reasons one might use PAM4_Mapping? MIPI C-PHY - Do we need changes in IBIS: Arpad started a discussion about whether we need to enhance the legacy IBIS buffer keywords to deal with MIPI C-PHY. He presented some schematic overviews of the MIPI C-PHY interface. Walter said each lane of MIPI C-PHY consists of 3 lines. Each of those lines is essentially a single-ended PAM3. The lines might have separate delays, etc., but the EDA tool could run 3 single-ended AMI simulations to the far end. There are rules about which combinations of levels are allowed on the 3 lines at a given time, but the EDA tool could control the stimulus input to the 3 PAM3 channel simulations to ensure compliance with those rules. Fangyi observed that the three driver states shown in Arpad's original schematic overview were 50 Ohms to one rail, 50 Ohms to the other rail, and 100 Ohms to each rail. We end up with a voltage source with 50 Ohm impedance, and the voltage source has 3 levels. IBIS could handle the 3 levels by varying the VCC. IBIS really only cares about the I/V curves. Arpad said AMI simulations were one thing, but they involve an LTI assumption. He asked whether we might need to enhance the keywords for non-AMI IBIS so we could address the MIPI C-PHY architecture and deal with non-linear effects like PDNs and modulation from supply effects. Walter said the question was whether we want to do any of this. - Curtis: Motion to adjourn. - Randy: Second. - Arpad: Thank you all for joining. AR: Arpad to send BIRD213.1 draft 25 to the ATM list. AR: Walter to alter draft 25 by creating a list of combinations and behaviors for PAM_Offsets Usage Rules. ------------- Next meeting: 24 May 2022 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives