Hi, Walter; Thank you for the explanation. One more question regarding getting rid of Use_Init_Output. Current spec says that if Use_Init_Output is False, GetWave_Exists must be True (1st line on page 8). If we remove Use_Init_Output from the parameters, does it mean GetWave_Exists is always True and all Tx and Rx models must implement GetWave? If this is the case, then we can get rid of GetWave_Exists too. Fangyi From: Walter Katz [mailto:wkatz@xxxxxxxxxx] Sent: Thursday, October 08, 2009 2:34 PM To: RAO,FANGYI (A-USA,ex1); ibis-macro@xxxxxxxxxxxxx Subject: RE: [ibis-macro] Re: Let me clarify the benifit of getting rid of Use_Init_Output along with Digital Input to Tx GetWave Fangyi, Arpad is exactly right. I defined the digital waveform as. | Step 4. The simulation platform produces a digital stimulus waveform. | A digital stimulus waveform is .5 when the stimulus is "high", | -.5 when the stimulus is "low", and may have a value between | -.5 and .5 such transitions occur when the stimulus crosses 0. Walter Walter Katz 303.449-2308 Mobile 720.333-1107 wkatz@xxxxxxxxxx www.sisoft.com -----Original Message----- From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]On Behalf Of Muranyi, Arpad Sent: Thursday, October 08, 2009 5:23 PM To: ibis-macro@xxxxxxxxxxxxx Subject: [ibis-macro] Re: Let me clarify the benifit of getting rid of Use_Init_Output along with Digital Input to Tx GetWave Yes, that's how you can position the exact location for the zero crossing to add jitter or DCD in finer resolution than the sampling time. Arpad ===================================================== ________________________________ From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of fangyi_rao@xxxxxxxxxxx Sent: Thursday, October 08, 2009 4:04 PM To: wkatz@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx Subject: [ibis-macro] Re: Let me clarify the benifit of getting rid of Use_Init_Output along with Digital Input to Tx GetWave Hi, Walter; I understand that the digital input swings between -0.5 and 0.5. Is the waveform allowed to have values between -0.5 and 0.5 during transition? Thanks, Fangyi From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz Sent: Tuesday, October 06, 2009 1:48 PM To: Ambrish Varma; IBIS-ATM Subject: [ibis-macro] Let me clarify the benifit of getting rid of Use_Init_Output along with Digital Input to Tx GetWave Ambrish, We have proven that the "Digital Input" to Tx GetWave is required. The whole concept of Use_Init_Output was introduced because Kumar and Cadence rejected requiring the model to implement the convolution of the impulse response of the Rx linear filter in the Rx GetWave. Kumar repeated his objection to doing this convolution in a recent IBIS-ATM meeting. If Use_Init_Output is True then the flow of using an externally generated waveform (e.g. Spice simulation) as input to the Rx GetWave is broken. It breaks the flow because the EDA tool is required to convolve the output of the Rx Init with the input to Rx GetWave. The input to Rx GetWave already contains the loss of the channel, so does the output of Rx Init. The argument that model writers are not capable to do this simple convolution is condescending to say the least. I would expect anyone who is capable of writing a model is capable of implement the code described in http://en.wikipedia.org/wiki/Overlap-save_method (Overlap-save algorithm for linear convolution) H = FFT(h,N) i = 1 while i <= Nx il = min(i+N-1,Nx) yt = IFFT( FFT(x(i:il),N) * H, N) y(i : i+N-M) = yt(M : N) i = i+N-M+1 end So if we get rid of Use_Init_Output, we do not need Init_Returns_Filter (although SiSoft will be generating models with this as a Model Specific Parameter, even if it does not become a Reserved Parameter). I have already spent many man months of effort on Analog Input to Tx GetWave, and Use_Init_Output, and frankly I do not want to spend any more time on it. Walter Walter Katz 303.449-2308 Mobile 720.333-1107 wkatz@xxxxxxxxxx www.sisoft.com