Arpad, In "ANY OTHER BACKGROUND INFORMATION" I state "The rise time of the step response voltage source should be as close to 0 as possible within the practical limits of SPICE simulations." (I added as possible) I changed the text at the bottom of the Transmitter Circuit to "The step response stimulus is a differential step response waveform which switch from a logic level 0 to a logic level 1.When logic level is 1, SRC1 V=Tx_V and SRC2 V=0. When logic level is 0, SRC1 V=0 and SRC2 V=Tx_V. The transition time between 0 and 1 in the two voltage sources is zero (or as close to zero as possible within the limitations of SPICE)." I am working with the graphic artist (Mike LaBonte) to fix the voltage source symbols. Walter From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Monday, May 20, 2013 3:26 PM To: 'IBIS-ATM' Subject: [ibis-macro] Re: BIRD 158.2 Walter, Regarding the notation of the voltage sources in the Tx drawing, I tend to agree with Bob. I does NOT reveal what you are stating: "The differential waveform is Tx_V-0 = Tx_V when high and 0-Tx_V when low. So the differential waveform is centered around 0." Now that I know your answer, I can force myself to "see" what you are saying in your notation "Tx_V,0" and "0,Tx_V" if I think of the HSPICE syntax for their "PULSE source", where the argument list of that particular source type contains a starting voltage, a comma, and the pulse voltage among many other arguments. Unfortunately it is not obvious that this drawing uses a portion of the HSPICE PULSE source syntax, and an uninitiated reader can get confused just like Bob and I got confused reading this drawing. The other problem is that the text below the drawing contradicts even this interpretation of the drawing. For one, the use of "Vdc" is inappropriate because this is not a DC source. But more importantly, the text explicitly says that the pulse is between zero and Tx_V volt for both sources. This doesn't seem to support the idea that there is a differential stimulus with levels of +/- Tx_V, centered around 0 volts. This needs to be cleaned up. While I am at it, how do you propose to implement a zero rise/fall time in a time domain simulation? I think the BIRD should say something about that too. Thanks, Arpad =================================================================== From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz Sent: Friday, May 17, 2013 9:36 PM To: 'Bob Ross' Cc: 'IBIS-ATM' Subject: [ibis-macro] Re: BIRD 158.2 Bob, Comments in-line, I sent (and attached this time BIRD 158.2) to the reflector Walter From: Bob Ross [mailto:bob@xxxxxxxxxxxxx] Sent: Friday, May 17, 2013 8:56 PM To: wkatz@xxxxxxxxxx Cc: 'IBIS-ATM' Subject: RE: [ibis-macro] BIRD 158.2 Walter: I did not see the draft BIRD158.2 attachment, but attached are some editorial corrections to the content of BIRD158.1. We can go over them at the ATM meeting. The port 1 waveform is documented as __ __| V = Tx_V,0, but should be V = 0, Tx_V Similarly for ___ |__ should be V = Tx_V, 0 The words in the text are independent of the diagram. (I cannot edit the diagram.) My questions/comments are 1. I am not happy that we have to introduce a common mode offset in contradiction to page 164, Step 4 of the Specification which states that the input voltages are from -0.5 to 0.5. WMK> You are comparing apples and oranges. The differential waveform is Tx_V-0 = Tx_V when high and 0-Tx_V when low. So the differential waveform is centered around 0. I think it would be better to introduce Tx_Vp and Tx_Vn where Tx_Vp defaults to 0.5V and Tx_Vn defaults to -0.5, and the differential input is from V= Tx_Vn, Tx_Vp on port 1 and V = Tx_Vp, Tx_Vn on port 2. Then the parameters can be passed in directly into the Converter Parameters of BIRD160 to specify a differential stimulus that spans -0.5 to 0.5. The common mode offset is disturbing and assumes no common-mode to differential conversions. Alternatively, we could enter in Tx_Vp and Tx_Vn to match the actual voltage swing limits in the physical Tx buffer. Also the Definition of V_Tx is strange: "defines the rail voltage of the I/O power supply in volts". Are we really defining a power supply voltage or a voltage swing limit? Corners are already in sync, but I would rather put the burden of syncing up Tx_Vp and Tx_Vn values on the EDA tool than to create a technically unnecessary offset due to weaknesses in other parts of the specification. WMK> This is more realistic. In a normal differential driver both the positive and negative side swing typically between 0V and PuRef. Thus one can think of Tx_V as PuRef. When the input to the Tx is an equalized waveform (e.g. output of Tx GetWave), then in affect the algorithmic model is modulating PuRef. I think we have heard these exact words from David. 2. Should the Tstonefile name be changed to Tstonefile_s4p since this if a pre-defined file for S-parameter 4-ports only? Other predefined Tstonefile configurations are possible now and in the future (for S, Y, Z parameters or for a different number of ports). To "Tstonefile" seems too generic when it applies to a specific configuration. WMK> I used Tstonefile because this is the name that IBIS-ISS uses, I see no need to change this. 3. Will the BIRD158 Reserved Parameters work without BIRD160? WMK> Yes Bob From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz Sent: Friday, May 17, 2013 3:45 PM To: Michael Mirmak Cc: IBIS-ATM Subject: [ibis-macro] BIRD 158.2 MM, I am formally submitting BIRD 158.2 to the Open Forum and requesting that a vote be taken at the next Open Form to approve this BIR for inclusion in the next release of IBIS. I have made the change to specifically state that the Touchstone specified by the reserved AMI parameter Tstonefile does not include the IBIS package model, and described one method of generating an Impulse Response of the channel suitable for use as input to the Tx AMI_Init function. I have not made the change to the graphic that Bob requested because I do not know how, because I think it is unimportant since the words in the text describe exactly what to do, and because it can be done as part of the editorial review. I will re-submit this BIRD if required due to any editorial changes made during the Tuesday IBIS-ATM meeting. Walter Walter Katz wkatz@xxxxxxxxxx Phone 303.449-2308 Mobile 303.335-6156
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