Just notice that the attached document in the previous email didn't go throught. Please check the following link for the document. http://www.doe.carleton.ca/~cchen/download/Pre_De_emphasis.doc It is appreciated if someone can provide me the implementation block diagrams for both pre-emphasis and de-emphasis. Thanks. Adiu --- On Mon, 11/2/09, Lee Ritchey <leeritchey@xxxxxxxxxxxxx> wrote: From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx> Subject: [SI-LIST] Re: what's de-emphasis To: "Istvan Novak" <istvan.novak@xxxxxxx>, "Adiu" <adiu_panli@xxxxxxxxx> Cc: "LY" <long.0.yang@xxxxxxxxx>, "Bill Wurst" <billw@xxxxxxxxxxx>, "prasad" <hariprasad.palli@xxxxxxxxx>, Joseph.Schachner@xxxxxxxxxx, si-list@xxxxxxxxxxxxx Received: Monday, November 2, 2009, 1:23 PM Istvan, Well put. For accuracy, the first is preemphasis. Lee > [Original Message] > From: Istvan Novak <istvan.novak@xxxxxxx> > To: Adiu <adiu_panli@xxxxxxxxx> > Cc: LY <long.0.yang@xxxxxxxxx>; Bill Wurst <billw@xxxxxxxxxxx>; prasad <hariprasad.palli@xxxxxxxxx>; <Joseph.Schachner@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Date: 11/2/2009 5:45:58 AM > Subject: [SI-LIST] Re: what's de-emphasis > > Adiu, > > In terms of resulting waveform shapes, preemphasis and deemphasis in > SerDes are identical. The differentiator is what is your baseline: if > your reference level is the steady state and you boost the first > transition bit, it is called deemphasis. If the level of your first > transitioning bit is the reference and you decrease the level of > subsequent bits, it is called deemphasis. The difference matters only > for the cell design, for the user they should be identical. > > Regards, > > Istvan Novak > SUN Microsystems > > > > > Adiu wrote: > > Thanks for all replies. > > > > My application of this pre/de-emphasis is SerDes signals. > > It is more clear to me now that pre/de-emphasis functions similarly > > (the pulse waveform shape looks same), except that de-emphasis > > produces smaller amplitude. > > > > However, going to the implementation details, I still have some concerns. > > To explain my concerns more clearly, I am attaching a one-page word > > document. > > In the document, > > First, an arbitrary 1v nominal waveform is shown. > > Second, the pre-emphasis implementation block digaram captured from a > > Altera document is shown. > > Third, the pre-emphasis waveform obtained based on the Altera > > implementation diagram is shown. my concern: this waveform seems to me > > more like the de-emphasis waveforms based on the dicussion. > > Fourth, I try to plot the pre-emphasis waveform based on the > > discussion. my concern: is this correct? > > > > Could any one provide me the block implementation diagrams for both > > pre-emphasis and de-emphasis? > > > > Thanks again for everyone's time. > > > > Best regards, > > Adiu > > > > --- On *Sun, 11/1/09, Istvan Novak /<istvan.novak@xxxxxxx>/* wrote: > > > > > > From: Istvan Novak <istvan.novak@xxxxxxx> > > Subject: Re: [SI-LIST] Re: what's de-emphasis > > To: "LY" <long.0.yang@xxxxxxxxx> > > Cc: "Bill Wurst" <billw@xxxxxxxxxxx>, "Adiu" > > <adiu_panli@xxxxxxxxx>, "prasad" <hariprasad.palli@xxxxxxxxx>, > > Joseph.Schachner@xxxxxxxxxx, si-list@xxxxxxxxxxxxx > > Received: Sunday, November 1, 2009, 10:25 PM > > > > If you search the SI-list archives you should find past > > discussions on > > this same topic with more detailed explanations. > > > > LY wrote: > > > Istvan: > > > Could you make it clear about the pre/de-emphasis in > > > telecommunications and SerDes signaling? > > > > > > Long Yang > > > Joan Crawford - "I, Joan Crawford, I believe in the dollar. > > > Everything I earn, I spend." - > > > http://www.brainyquote.com/quotes/authors/j/joan_crawford.html > > > > > > > > > On Mon, Nov 2, 2009 at 08:13, Istvan Novak <istvan.novak@xxxxxxx > > <http://ca.mc354.mail.yahoo.com/mc/compose?to=istvan.novak@xxxxxxx>> > > wrote: > > > > > >> Bill and All, > > >> > > >> Rather than saying that this definition is wrong, we should say > > that > > >> this does not apply to digital SerDes signaling. > > >> If one reads the entire text on wikipedia, it is clear that it > > refers to > > >> telecommunications applications, where the high- > > >> frequency components are in fact suppressed. The unfortunate > > fact is > > >> that deemphasis means different things in > > >> telecommunications and in SerDes signaling. > > >> > > >> Regards, > > >> > > >> Istvan Novak > > >> SUN Microsystems > > >> > > >> > > >> Bill Wurst wrote: > > >> > > >>> Adiu, > > >>> > > >>> As Joe S. indicated, the definition for de-emphasis is clearly > > wrong. A > > >>> more correct way of stating de-emphasis would be: > > >>> De-emphasis: Improving the signal to noise ratio by > > >>> decreasing the magnitude of lower frequency signals > > >>> with respect to higher frequency signals. > > >>> Even with this corrected definition, you will note that what both > > >>> pre-emphasis and de-emphasis accomplish is similar. Thus, > > given the > > >>> same input waveshape, the waveforms output from either process > > will have > > >>> the same shape. > > >>> > > >>> Either pre-emphasis or de-emphasis is usually accomplished at the > > >>> transmitter, while equalization is done at the receiver. > > Although all > > >>> three work in different ways, they all accomplish the same > > purpose, > > >>> i.e., to flatten the frequency response of the overall system by > > >>> compensating for distortions introduced by the transmission > > medium. > > >>> > > >>> Best regards, > > >>> -Bill > > >>> > > >>> /************************************ > > >>> / William C. Wurst, PE / > > >>> / billw@xxxxxxxxxxx > > <http://ca.mc354.mail.yahoo.com/mc/compose?to=billw@xxxxxxxxxxx> > > / > > >>> / Advanced Electronic Concepts, LLC / > > >>> / www.aec-lab.com / > > >>> ************************************ > > >>> ========================================================= > > >>> prasad wrote: > > >>> > > >>> > > >>>> i believe, its a matter of reference with which we are > > defining. since the > > >>>> technique is much evident when we see frequent transitions, > > the amplitude of > > >>>> those bits is higher than the bits having the lesser > > transitons. extending > > >>>> this to a combination of lets say, 0111, the transtion from 0 > > to 1 will have > > >>>> higher amplitude than the further 1s. so we say that 0to 1 is > > pre emphasized > > >>>> or 1to 1 is deemphasized w r t 0 to 1. > > >>>> > > >>>> > > >>>> > > >>>> 2009/10/31 <Joseph.Schachner@xxxxxxxxxx > > <http://ca.mc354.mail.yahoo.com/mc/compose?to=Joseph.Schachner@xxxxxxxxxx>> > > >>>> > > >>>> > > >>>> > > >>>>> Of the two definitions you got from Google: > > >>>>> Pre-emphasis: " Improving the signal to noise ratio by > > increasing the > > >>>>> magnitude of higher frequency signals with respect to lower > > frequency > > >>>>> signals" > > >>>>> De-emphasis: " Improving the signal to noise ratio by > > decreasing the > > >>>>> magnitude of higher frequency signals with respect to lower > > frequency > > >>>>> signals" > > >>>>> > > >>>>> > > >>>>> The Pre-emphasis definition is acceptable. The De-emphasis > > definition is > > >>>>> clearly wrong, in my opinion. De-emphasis goal is the same, > > to increase > > >>>>> magnitude of higher frequency signals with respect to low > > frequency > > >>>>> signals. It just is a slightly different way to get that > > effect. > > >>>>> > > >>>>> I think pre-emphasis and de-emphasis are much easier to > > understand in the > > >>>>> time domain, rather than the frequency domain. > > >>>>> In the time domain, as text with with one dash per UI > > (transitions don't > > >>>>> appear) : > > >>>>> Each diagram is 4 UI low, 5 UI high, 4 UI low > > >>>>> _ > > >>>>> _____ ... ____ ... _ > > >>>>> ____ > > >>>>> ____ ____ ... ____ ___ ... ____ ___ > > >>>>> _ _ > > >>>>> > > >>>>> The desired pulse With pre-emphasis With deemphasis > > >>>>> The first UI All but the first UI > > >>>>> after a transition after a transition > > >>>>> is higher amplitude are lower amplitude > > >>>>> > > >>>>> > > >>>>> The reason to do this is because a normal channel attenuates > > high > > >>>>> frequencies more, > > >>>>> so the (relatively) sharp rising edge of a transmitted pulse > > will become > > >>>>> slower > > >>>>> at the far end, and the first UI would not reach the desired > > height by the > > >>>>> middle > > >>>>> of the UI. That is, it would cause the eye opening to be > > reduced. > > >>>>> By having the TX pump out a larger transition, after the > > loss due to the > > >>>>> channel, > > >>>>> at the far end, the signal looks better - more like what we > > desired. > > >>>>> Standards > > >>>>> like PCI-Express don't actually call for pre-emphasis, > > rather they call for > > >>>>> de-emphasis. The effect is the same - the transitions are > > sent larger than > > >>>>> subsequent bits; but it is achieved by using the nominal > > level for the > > >>>>> first bit > > >>>>> after a transition and a smaller level for all subsequent > > bits. This makes > > >>>>> a nice > > >>>>> but smaller eye. > > >>>>> > > >>>>> --- Joe S. > > >>>>> > > >>>>> > > >>>>> Adiu wrote: > > >>>>> > > >>>>> > > >>>>>> Hello, Everyone > > >>>>>> > > >>>>>> What's pre-emphasis and de-emphasis? > > >>>>>> I can get the following definitions from Google: > > >>>>>> > > >>>>>> Pre-emphasis: " Improving the signal to noise ratio by > > increasing the magnitude of higher frequency signals with respect > > to lower frequency signals" > > >>>>>> De-emphasis: " Improving the signal to noise ratio by > > decreasing the magnitude of higher frequency signals with respect > > to lower frequency signals" > > >>>>>> > > >>>>>> There is not problem to understand the above definitions. > > However, I have difficulities in the following concerns: > > >>>>>> 1. is pre-emphasis always at the transmitter? > > >>>>>> 2. is de-emphasis always at the receiver? > > >>>>>> 3. what's difference between de-emphasis and equalization? > > >>>>>> 4. I have not problems to draw the pre-emphasis pulse > > waveforms with respect to a normal waveform. However, I am not > > quite sure of the de-emphasis pulse waveforms. The attached figure > > shows a simple example. Could someone confirms for me if the > > waveforms are draw correctly? > > >>>>>> > > >>>>>> any comments are appreciated. > > >>>>>> > > >>>>>> best regards, > > >>>>>> adiu > > >>>>>> > > >>>>>> > > >> ------------------------------------------------------------------ > > >> To unsubscribe from si-list: > > >> si-list-request@xxxxxxxxxxxxx > > <http://ca.mc354.mail.yahoo.com/mc/compose?to=si-list-request@xxxxxxxxxxxxx> > > with 'unsubscribe' in the Subject field > > >> > > >> or to administer your membership from a web page, go to: > > >> //www.freelists.org/webpage/si-list > > >> > > >> For help: > > >> si-list-request@xxxxxxxxxxxxx > > <http://ca.mc354.mail.yahoo.com/mc/compose?to=si-list-request@xxxxxxxxxxxxx> > > with 'help' in the Subject field > > >> > > >> > > >> List technical documents are available at: > > >> http://www.si-list.net <http://www.si-list.net/> > > >> > > >> List archives are viewable at: > > >> //www.freelists.org/archives/si-list > > >> or at our remote archives: > > >> http://groups.yahoo.com/group/si-list/messages > > >> Old (prior to June 6, 2001) list archives are viewable at: > > >> http://www.qsl.net/wb6tpu > > >> > > >> > > >> > > >> > > > > > > > > > > > > ------------------------------------------------------------------------ > > > > *Yahoo! 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