Raja, > 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. > If am not mistaken, I would open the file stream as binary and then I would do as follows: /* getbits: get n bits from position p */ unsigned getbits(unsigned x, int p, int n) { return ((x >> (p+1-n)) & ~(~0 << n)); } The above function is found in The C Programming Language by Brian W. Kernighan and Dennis M. Ritchie, 2nd Edition. ... char c; unsigned char lsb, hsb; FILE* fstream = fopen(filename, "rb"); if (fstream == NULL) return (EXIT_FAILURE); while (feof(fstream == 0) { (void)fread(&c, sizeof (char), (size_t)1, fstream); /* getbits(x, p, n) */ lsb = getbits(c, 5, 3); hsb = getbits(c, 0, 5); /* do what you must with lsb and hsb */ ... } return (EXIT_SUCCESS); Efren Serra > 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 ------------------------------------------------------------------ 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