IBIS Macromodel Task Group Meeting date: 26 March 2024 Members (asterisk for those attending): Achronix Semiconductor: Hansel Dsilva Amazon: John Yan ANSYS: * Curtis Clark * Wei-hsing Huang Aurora System: Dian Yang Raj Raghuram Cadence Design Systems: * Ambrish Varma * Jared James Dassault Systemes: Longfei Bai Google: Hanfeng Wang GaWon Kim Intel: * Michael Mirmak Kinger Cai Chi-te Chen Liwei Zhao Alaeddin Aydiner Keysight Technologies: Fangyi Rao Majid Ahadi Dolatsara Stephen Slater Ming Yan Rui Yang Marvell: Steve Parker Mathworks (SiSoft): Walter Katz Graham Kus Micron Technology: Justin Butterfield Missouri S&T: Chulsoon Hwang Yifan Ding Zhiping Yang Rivos: Yansheng Wang SAE ITC: Michael McNair Siemens EDA (Mentor): * Arpad Muranyi * Randy Wolff 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: Michael: Submit the "Definitions Section" proposal to the Open Forum as an official BIRD. - Done. It was submitted as BIRD230. Michael: Send draft4 of the Block Clarification proposal 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 March 19th meeting. Michael moved to approve the minutes. Randy seconded the motion. There were no objections. -------------- New Discussion: Block Clarification proposal: Michael reviewed draft4 of the proposal, which he had sent to the ATM list on Wednesday March 20th. He said that it incorporated all of the changes from the previous meeting, and he had received no new feedback. Michael noted one editorial issue. He said a half-sentence had been left at the beginning of the Background Information/History section and should be removed. Arpad asked whether the proposal was ready to send to the Open Forum. Michael moved to submit draft4 (with the editorial correction) to the Open Forum. Jared seconded. There were no objections. Fixing [Clock Pins]: Michael reviewed a presentation on the limitations of the [Clock Pins] keyword. In 2021, BIRD208 introduced [Clock Pins] into IBIS 7.1. Michael said the original intent of [Clock Pins] was to specify which clock pins latch which data pins. A third column provides a string that could be used to define the timing relationship, though the only allowed value as of IBIS 7.2 is "Unspecified". A limitation of [Clock Pins], which was only recognized after BIRD208 was approved, is that the clock pin to data pin relationships are fixed and defined at the time the .ibs file is created. Therefore, controllers are not easily supported. A controller might have multiple modes. A single clock line might support 4 data lines (nibble) in one mode and support 8 data lines (byte) in another mode. Michael noted that [Pin]s may have [Model Selector]s. He said we need an analogous clock selector. Michael proposed a new solution that repurposes the third column in the [Clock Pins] keyword. The third column could contain a value indicating a grouping, which could serve as a clock selector. Michael reviewed a [Clock Pins] example illustrating the nibble and byte cases in the same [Clock Pins] keyword using different "x4" and "x8" groupings. [Clock Pins] clocked_pins relationship A1 B1 x4 | Pins B1, B2, B3, B4 use clock information from A1 A1 B2 x4 | and can be organized as x4 A1 B3 x4 A1 B4 x4 A2 B5 x4 | Pins B5, B6, B7, B8 use clock information from A2 A2 B6 x4 | and can be organized as x4 A2 B7 x4 A2 B8 x4 | A1 B1 x8 | Pins B1, B2, B3, B4 A1 B2 x8 | B5, B6, B7, B8 use clock information from A1 A1 B3 x8 | and can be organized as x8 A1 B4 x8 A1 B5 x8 A1 B6 x8 A1 B7 x8 A1 B8 x8 Michael said this would be legal with the existing definition of [Clock Pins], except for the fact that "Unspecified" is currently the only allowed value in column 3. Arpad asked whether [Model Selector]s themselves could cause problems for the timing relationship specifications. Could choosing a different [Model] for a [Pin] affect the timing relationships we want to define with [Clock Pins]? Michael said he didn't think that would affect the clock pin to data pin relationship being defined by the clock selector, but it might be possible that a selected [Model] would fail to meet some timing requirements for that relationship. He noted that we hadn't yet gotten to the point of specifying any timing requirements. Michael said we would remove the following sentence from IBIS 7.2, if we adopt his proposed change to the usage of the third column: The structure of [Clock Pins] assumes that the clocking relationships cannot be redefined dynamically for the given [Component] (for example, the number of data pins supported by any one clock pin is fixed). Arpad said we have to be careful about the language. Even with the proposed change, we still won't support dynamically changing the clocking relationships during simulation. We will allow the selection of a configuration prior to a given simulation. Michael said that one possible drawback to his proposal is that using the third column as group/clock selector might conflict with the original intent of specifying the actual timing relationships (e.g., clock skews, etc.). Michael closed with a call for feedback. He said the larger questions still remaining are what timing relationships to specify and how to specify them. Can we use values, or do we need equations? How do we reference expected timing relationships but handle manufacturing variations or variable configurations? How do we reference timing relationships that are strict requirements to enforce? Ambrish asked whether there was any precedent for having this type of timing information in IBIS. He asked whether this information should come from a higher level protocol or system specification. Michael replied that Vinh and Vinl fulfill a similar purpose, although in a much more simplistic manner. The goal is to provide additional information useful for evaluating whether an interface is working. - Michael: Motion to adjourn. - Ambrish: Second. - Arpad: Thank you all for joining. New ARs: None. ------------- Next meeting: 02 April 2024 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives