Hi List members, Thanks for the educative discussion on 8b10b. If I mistake not, we were taught that DC balance is required to prevent X-mer saturation (and I am NOT 100 yrs old). Then I see this DC balance again coming up in Fibre channel discussions and I was puzzled. As usual (and most conveniently) I blamed it on Mr. Bill Gates(I mean the ctrl+C => ctrl+V methodology) but looks like there is another aspect to it which has/had nothing to do with a X-mer. Folks blame it on my Prof, I had been a good student! May be believed a bit too much in those guys. Okay so, I again read about the encoding and still not able to understand it. I mean you take 8 bits, then split them in lower 5 and upper 3. Then you write them as /Dx.y/ where x is the decimal value of ...Then you have comma character..and somewhere I am lost. Ref: http://www.iol.unh.edu/training/ge/8B10BEncoding.html Okay the que is: If I am to write a C/Matlab code for converting a *raw* data to 8b10b encoded data what exactly I need to do? or in other words, Pat how did you *look at* the spetrum of raw and encoded data. How did you generate both the streams? I hope C/Matlab are sufficient to get a feel for it. or was is it back-of-the-envelope calculation. Another thing: As is quite evident from my question, I am new to this field (come from Instru where we are concerned about low freq, drift etc. aspects) So I would like to know some book(s) which will introduce me to ISI, Jitter, Clock recovery and other such Networking/ Communication related physical layer signalling problems/phenomenon. Most of the books on Jitter are too mathematical to give a feel for the physical activity. Also what is this subject called? I searced "signalling" on Amazon.com w/o any luck. All/any comments appreciated. regards, - Raja -- On Wed, 12 Sep 2001 21:38:53 zanella, fabrizio wrote: > >We've been using serdes devices with 8b/10b encoding and phase locked loops, >and have found the PLLs to be very sensitive to low frequency noise (<2MHz) >at low VCC. Does anyone know if devices which use DLLs (delay locked loops) >are less sensitive to low frequency noise? >thanks, > >Fabrizio Zanella >Signal Integrity >EMC Corporation >508-435-2075, x14645 >fzanella@xxxxxxx > > >-----Original Message----- >From: Mike Jenkins [mailto:jenkins@xxxxxxxx] >Sent: Tuesday, September 11, 2001 8:50 PM >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: purpose of 8b/10b encoding > > >Pat, > >In addition to zero DC content and guaranteed transitions to which >a PLL can lock, 8B10B (that's the way IBM wrote it originally) code >has the string ...0011111... or it's inverse which occurs only as the >first 7 characters of a 10-bit character, making byte alignment to >these sync characters easy. Alignment for more efficient codes (e.g., >64b/66b) is much more complex and statistical. > >The spectral content comes from limiting "running disparity" (the >ratio of 0's to 1's) which limits the low frequency content more >than, say, scrambled data, allowing the use of smaller blocking >capacitors. (At these high frequencies, good capacitors with large >values are not cheap, if they can be gotten at all.) > >Lastly, 6B10B also provides a reasonably high error detection >capability. > >Besides Infninband, 8B10B has been selected by Fibre Channel, 1G and >10G Ethernet, SerialATA, 3GIO, and, I suspect, more. Some of the >popularity may be momentum, but that's a lot of people going through >the same cost/benefit analysis as you. They all decided it was worth >the costs. > >Regards, >Mike > > >"Zabinski, Patrick J." wrote: >> >> Jeffrey, >> >> Thanks for the feedback. >> >> Looking at the spectrum of an un-encoded/raw data stream versus >> an 8b/10b-encoded data stream, I can see how the power >> spectral density will be increased at a frequency >> equal to the data rate/2, which would provide more >> information for a PLL to synch onto. >> >> If this is the case, is there a way of analyzing exactly how >> much better a PLL can synch when using 8b/10b vs when >> not using 8b/10b? If there is, can the analysis be >> generalized to allowing me to determine how often >> transitions need to be in order for a PLL to lock? >> >> Thanks, >> Pat >> >> > >> > # What's the purpose of 8b/10b encoding? >> > >> > Generally as I understand, it is to be able to recover the clock by >> > ensuring some number of transitions per period (8 per 10?). >> > Clocks change >> > period frequently when working at high speeds, due to >> > temperature, etc... not >> > to meantion the fact that otherwise the sending clock would >> > inevitably be >> > out of phase, plus period, of your receiver's clock. >> > >> > >> ------------------------------------------------------------------ >> To unsubscribe from si-list: >> 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 with 'help' in the Subject field >> >> 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 >> > >-- >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Mike Jenkins Phone: 408.433.7901 _____ > LSI Logic Corp, ms/G715 Fax: 408.433.7495 LSI|LOGIC| (R) > 1525 McCarthy Blvd. mailto:Jenkins@xxxxxxxx | | > Milpitas, CA 95035 http://www.lsilogic.com |_____| >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~pc > > >------------------------------------------------------------------ >To unsubscribe from si-list: >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 with 'help' in the Subject field > >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 > >------------------------------------------------------------------ >To unsubscribe from si-list: >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 with 'help' in the Subject field > >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 > > > Get 250 color business cards for FREE! http://businesscards.lycos.com/vp/fastpath/ ------------------------------------------------------------------ To unsubscribe from si-list: 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 with 'help' in the Subject field 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