Bob, Thanks. Update version enclosed. Walter From: Bob Ross [mailto:bob@xxxxxxxxxxxxx] Sent: Monday, May 20, 2013 7:53 PM To: wkatz@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx; 'IBIS-ATM' Subject: RE: [ibis-macro] Re: BIRD 158.2 Walter: Here are some more editorial corrections to accommodate BIRD160 and to deal with Steps: declarations of type Output à declarations of type Output or Output_diff declarations of type Input à declarations of type Input or Input_diff Step à Steps (I forgot that the differential input spans 2*Tx_V, as currently configured.) Bob From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz Sent: Monday, May 20, 2013 2:20 PM To: Arpad_Muranyi@xxxxxxxxxx; 'IBIS-ATM' Subject: [ibis-macro] Re: BIRD 158.2 Arpad, First, I am including 158.4 which has the graphic for the step response voltage source as Bob requested. You are confusing the waveform input to Tx GetWave which is differential (centered around 0.0V) with the single ended half of a differential signal. In this example (as in most differential signaling), both the non-inverting and inverting side of a differential typically go between ~0.0 Volts and ~PuRef. These are the SINGLE ENDED voltage swings. The differential voltage goes between PuRef and PuRef. In fact the common mode voltage goes away in AMI modeling because we only deal with DIFFERENTIAL impulse responses and DIFFERENTIAL waveforms. Again you are comparing apples and oranges. In differential signaling single ended waveforms may and in fact usually do have common mode components. AMI modeling currently ignores the common mode component in its algorithmic modeling. Of course there is common mode to differential conversion in the analog (e.g. step response simulation) so common mode must be accommodated in the single ended signals) and in generating the impulse response of the channel. AMI makes the basic assumption that the Rx does an excellent job of common mode rejection. I cannot attest to the validity of this assumption, other than this is the assumption made in many IC Vendor internal analysis tools. Walter From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Monday, May 20, 2013 4:06 PM To: 'IBIS-ATM' Subject: [ibis-macro] Re: BIRD 158.2 Walter, That added sentence doesnt change anything in the voltage values you defined for the two sources. The step response stimulus is a differential step response waveform which switch from a logic level 0 to a logic level 1. The next sentence still defines your differential stimulus with a DC component of Tx_V/2 away from the axis because the high and low levels of the sources are Tx_V and 0 V, which averages to Tx_V/2. So the question is this, do you intentionally want this stimulus to have a DC component of Tx_V/2 and want to be inconsistent with the +/-0.5 volt stimulus defined for the AMI bit pattern? Thanks, Arpad ======================================================== From: Walter Katz [mailto:wkatz@xxxxxxxxxx] Sent: Monday, May 20, 2013 2:50 PM To: Muranyi, Arpad; 'IBIS-ATM' Subject: RE: [ibis-macro] Re: BIRD 158.2 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 doesnt 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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