IBIS Macromodel Task Group Meeting date: 28 May 2013 Members (asterisk for those attending): Agilent: * Fangyi Rao * Radek Biernacki Altera: * David Banas Julia Liu Hazlina Ramly Andrew Joy Consulting: Andy Joy ANSYS: Samuel Mertens * Dan Dvorscak * Curtis Clark Steve Pytel Luis Armenta Arrow Electronics: Ian Dodd Cadence Design Systems: Terry Jernberg * Ambrish Varma Feras Al-Hawari Brad Brim Kumar Keshavan Ken Willis Cavium Networks: Johann Nittmann Celsionix: Kellee Crisafulli Cisco Systems: Ashwin Vasudevan Syed Huq Ericsson: Anders Ekholm IBM: Greg Edlund Intel: * Michael Mirmak Maxim Integrated Products: Mahbubul Bari * Hassan Rafat Ron Olisar Mentor Graphics: * John Angulo Zhen Mu * Arpad Muranyi Vladimir Dmitriev-Zdorov Micron Technology: Randy Wolff Justin Butterfield NetLogic Microsystems: Ryan Couts Nokia-Siemens Networks: Eckhard Lenski QLogic Corp. James Zhou SiSoft: * Walter Katz Todd Westerhoff Doug Burns * Mike LaBonte Snowbush IP: Marcus Van Ierssel ST Micro: Syed Sadeghi Teraspeed Consulting Group: Scott McMorrow * Bob Ross TI: Casey Morrison Alfred Chong Vitesse Semiconductor: Eric Sweetman Xilinx: Mustansir Fanaswalla Ray Anderson The meeting was led by Arpad Muranyi ------------------------------------------------------------------------ Opens: - Arpad: Our agenda is full, we should try to avoid getting stuck - David: There were emails on BIRD 158.3, we should leave time for that -------------------------- Call for patent disclosure: - None ------------- Review of ARs: - Fangyi submit updated BIRD 156 to Open Forum - Done - Mike post update BIRD 156 to ATM web - Submitted to open forum instead ------------- New Discussion: Interconnect Task Group report: - Michael M: - EMD document review was tabled, we did a summit review instead. - Some scrubbing needs to be done on terminology. - We will be revisiting BIRD 161.1 next week. - Arpad: Should BIRD 161.1 be discussed in this meeting? - Michael M: We can keep it in the interconnect group until further notice - It probably will miss IBIS 6 either way. BIRD 158: - Arpad showed BIRD 158 - Bob: I think there is confusion on what the input is. - Arpad: There was a contradiction in defining the unit step. - Walter updated this, but Radek had an email comment on it. - Radek: The step response is a measurement taken with a unit step input. - The source voltages really are controlled by other unit step sources - It is not made clear that the sources shown only scale the input. - David: The rise time is called instantaneous, then it is admitted that that is impossible. - It should say the step rise time is one sample interval. - Mike L: Should it be "simulator time step"? - Fangyi: The simulator may have a coarser time step than the sample step. - David: The vector going into the simulation is what matters. - Walter: This discussion is independent of BIRD 158. - David: The BIRD discusses this, so it is relevant. - Walter: It is a generic problem, but BIRD 158 is the only place it is discussed. - There are other methods to generate an impulse response. - If not in BIRD 158, IBIS should discuss impulse response generation somewhere. - Radek: It is a separate issue and should have a separate BIRD. - Todd: Fangyi said the step goes in, but we read the response as an output. - For example 10Gbs at 8samples/bit would send 80G samples/sec to AMI_Init. - This is an impulse response, not delta-Dirac. - I can derive the response using any bandwidth I want. - Walter: That is 12.5ps time step, but the SPICE simulation may have 1ps time step. - Arpad: David was talking about the case where the simulation time step is coarser. - David: No one would ever characterize a channel at lower bandwidth than what is passed to AMI_Init. - Todd: This is not specific to BIRD 158, it is a generic problem. - Fangyi: The simulator does not need to put in a small time step based on calculated bandwidth. - David: How do we set a limit on bandwidth without over-constraining? - Todd: The data sent to the model requires a certain interval, and we assume it is valid. - Arpad: The [Model] keyword has no limit on voltage. - Should we have defined a unit step response? - Radek: The sources shown in the diagram as not necessarily the excitation. - There should be an input controlling these sources. - Arpad: The analog model should be characterized with EQ off. - This BIRD is consistent with that. - Todd: We use "step response" and "impulse response" imprecisely. - AMI responses are not mathematical responses. - The request here is to have that shown explicitly. - David: I think we only need to talk about magnitude units. - Bob: Is this talking about voltages or scaling? - Radek: It would be the actual voltage. - The picture just needs to be explained. - Arpad: The gain scaling could be put in the s-parameter too. - Todd: When we worked with Agilent a year ago we thought scaling outside the s-parameter would be easier - Arpad: I agree with Radek that the wording needs to be more precise. - Walter: We also have to support process corners. - Where the voltage is the only difference it is convenient to have scaling outside the s-parameter. - Todd: It would be best to avoid the term "step response". - Walter: The BIRD uses the term "Step Response Stimulus" to differentiate. - Fangyi: Yes that is important. - Also an IBIS [Model] is still driven by an event. - Todd: A lossy network will not produce a response with area = 1. - Walter: Wikipedia distinguishes between an impulse response and unit impulse response. - An impulse response simply maintains its area. - A unit response is the special case with area 1. - Radek: There was also an issue about common mode. - Walter: Where the TX and RX operate at different voltages the RX may be operated outside its linear region. - The Touchstone output should be able to mimic what legacy IBIS does. - Radek: The analysis ignores common mode. - Arpad: If operated at the wrong voltage the response may be wrong. - Radek: The ground is not clear and it may change. - Todd: Customers want plug and play. - If the receiver is HSPICE the waveform may be nonsense if biased wrong. Arpad showed the Redriver BIRD 156: - Arpad: Do we need the word "units" near "volts"? - Also should resampling consider the RX_Receiver_Noise value? - Todd: We have no "X" state here, only 0 and 1. - The PLL can't adapt that fast. - Arpad: Without a sensitivity range the state changes immediately above and below zero. - Walter: The sampling happens 1/2 UI after clock ticks. - Todd described a voltage/time scenario. - Walter: Only the voltage at clock tick times matter, not transitions. - Otherwise there would be a jitter problem. - Todd: This is an example why having the model do processing makes sense. - That allows for sublink error analysis. ------------- Next meeting: 04 June 2013 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives