David, Are you perhaps confusing "impulse" with "pulse" response? Please clarify your question... Thanks, Arpad ===================================== From: David Banas [mailto:DBanas@xxxxxxxxxx] Sent: Tuesday, July 17, 2012 1:08 PM To: Muranyi, Arpad; 'IBIS-ATM' Subject: RE: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI Arpad, Could you provide some clarification, please? Are you saying that probing for a model's impulse response, by sending a {0, 1, 0, 0, ...} sequence into the AMI_Init() function is invalid? (I've been having good results with this technique, and you've got me worried that those results are invalid.) Of course, I understand that I may pick up some aliasing, if my sample rate is insufficient. But, other than that, it is a valid technique for probing a model's impulse response; isn't it? Thanks, -db From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> On Behalf Of Muranyi, Arpad Sent: Tuesday, July 17, 2012 10:40 AM To: IBIS-ATM Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI Dan, There are several issues that need to be considered in this topic. The biggest issue in my mind is the question of time step. An ideal step or impulse function has zero width. In time step based simulators the best we can do for a step function is a slope that is one time step wide, and for an impulse function two slopes (one up and one down) that are a total of two steps wide. No matter how small you make your time step, these functions are never going to be what they should be. This introduces errors and the amount of error will depend on the time step, which may depend on the EDA tool's internal algorithms. Regarding: "Another way to look at it would be to say that if a model writer intended for a model to work with an ideal impulse response, they could essentially ship and IBIS file that pretty much only contains a c-comp, "zeroed out" V-I tables, and sharp edge rate in the ramp data to make it a fairly ideal driver." This is basically a suggestion to implement an ideal step or impulse function generator in the IBIS [Model]. But where is the buffer's model then? You would either have to put the buffer's impedance model in series or in parallel with this function generator. And the C_comp would belong to the buffer's model, not the ideal function generator. But why would you go this route, when the EDA tool can do the function generator in the stimulus, and the model maker can do the model of the device in the IBIS [Model]? Thanks, Arpad ======================================================================= From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> On Behalf Of Dan Dvorscak Sent: Tuesday, July 17, 2012 11:49 AM To: IBIS-ATM Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI Hi all, Sorry to reply late to this thread. I had been keeping an eye out for it, but seem to have missed it. Per what Greg and Arpad were discussing, should it not be up to the model writer to decide whether or not an ideal or an IBIS-generated impulse response is to be used? My expectation would be that a given IBIS buffer that points to an AMI model will contain all of the IBIS analog model features that the model writer intends to be included in the channel characterization. In that sense if a user or EDA tool chooses to ignore any of those features they are using the model in a way that it was not characterized for. Another way to look at it would be to say that if a model writer intended for a model to work with an ideal impulse response, they could essentially ship and IBIS file that pretty much only contains a c-comp, "zeroed out" V-I tables, and sharp edge rate in the ramp data to make it a fairly ideal driver. Does that seem like a fair assessment? Thanks, -Dan On Wed, Jul 11, 2012 at 10:37 AM, Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx<mailto:Arpad_Muranyi@xxxxxxxxxx>> wrote: Greg, The IBIS specification is intentionally silent about how to generate the impulse response for the channel, because there are different ways to do it, and EDA vendors might want to use their own "smarts" to do it the "best" way. You are correct, if someone wants to extract such an "ideal" IR, you would only make use of the C_comp and the impedance provided by the I-V curve from the analog model. BIRD 120 doesn't give any more detail (or restrictions) on how to generate the impulse response. So the EDA tool is free to do it the way they think it is the best to do it. I hope this helps, Arpad =========================================================== From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>] On Behalf Of Gregory R Edlund Sent: Wednesday, July 11, 2012 9:15 AM To: 'IBIS-ATM'; ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI What if an EDA programmer wanted to discard the VT and ramp data and compute an "ideal mathematical" impulse response assuming a delta function? Is that allowed by BIRD 120? I took a quick look and didn't see anything specific about how to calculate the impulse response. In the "ideal mathematical" case, I would think all you need is C_Comp and some resistance extracted from the IV tables. Greg Edlund Senior Engineer Signal Integrity and System Timing IBM Systems & Technology Group 3605 Hwy. 52 N Bldg 050-3 Rochester, MN 55901 [Inactive hide details for "Walter Katz" ---07/11/2012 03:53:30 AM---I agree.]"Walter Katz" ---07/11/2012 03:53:30 AM---I agree. From: "Walter Katz" <wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>> To: <Arpad_Muranyi@xxxxxxxxxx<mailto:Arpad_Muranyi@xxxxxxxxxx>>, "'IBIS-ATM'" <ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>> Date: 07/11/2012 03:53 AM Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI Sent by: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> ________________________________ I agree. Walter From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Tuesday, July 10, 2012 11:44 PM To: IBIS-ATM Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI That is correct. Arpad ================ From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:%5Bmailto:ibis-macro-bounce@xxxxxxxxxxxxx%5D> On Behalf Of Mirmak, Michael Sent: Tuesday, July 10, 2012 6:07 PM To: Walter Katz Cc: IBIS-ATM Subject: [ibis-macro] Re: What part of Legacy IBIS is used by IBIS-AMI Walter, Thank you! So, someone using IBIS-AMI models with valid traditional data in a workflow should expect changes in the IBIS TX C_comp or V-t (or [Ramp]) data to have an impact on the results provided by the receiver in an IBIS-AMI-based flow, assuming nothing else changes? - MM From: Walter Katz [mailto:wkatz@xxxxxxxxxx]<mailto:%5Bmailto:wkatz@xxxxxxxxxx%5D> Sent: Tuesday, July 10, 2012 12:20 PM To: Mirmak, Michael Cc: IBIS-ATM Subject: What part of Legacy IBIS is used by IBIS-AMI MM, The Legacy part of an IBIS model is used to generate the Impulse Response of the channel. One method of generating the impulse response is to do a step response, and take the derivative of the waveform at the Rx input. A simulator uses a combination of the Tx [Voltage Range], C_Comp, IV, VT and Ramp data, and the Rx C_Comp and IV data. Of course, [External Model] can also be used by a simulator. The following required Tx IBIS fields are not used in the AMI flow: Vmeas The following required Rx IBIS fields are not used in the AMI flow: Vinl Vinh Walter Walter Katz wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx> Phone 303.449-2308<tel:303.449-2308> Mobile 303.335-6156<tel:303.335-6156> -- Daniel Dvorscak ANSYS, Inc. 67 South Bedford St. Suite 202E Burlington, MA 01803 Tel: 781.229.8900 x352 Fax: 781.229.8624 ________________________________ Confidentiality Notice. This message may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient, you are hereby notified that any use, disclosure, dissemination, distribution, or copying of this message, or any attachments, is strictly prohibited. If you have received this message in error, please advise the sender by reply e-mail, and delete the message and any attachments. Thank you.