[SI-LIST] Re: How to embedded and to deembedded the clock to serial signal, such as GE and PCI-E

  • From: "zheng qi" <qzheng.hb@xxxxxxxxx>
  • To: wzhou@xxxxxxxxxxx
  • Date: Wed, 5 Apr 2006 14:13:48 +0800

Refer to http://bwrc.eecs.berkeley.edu/classes/EE290C_S04/

I feel the third reason will have the most possibilities .because PLL is
more sensitive to low frequency noise . which is always the main part of
the noise of the supply .

Regards
zheng qi

************************************
qzheng@xxxxxxxxxxxxxxxx
<qzheng.hb@xxxxxxxxx >
2006-4-5
************************************

2006/4/5, Wei Zhou <wzhou@xxxxxxxxxxx>:
>
> Zhangkun,
>
> A typical serial link like PCIE, GE have a PLL on the TX side and a clock=
 data recovery circuit (CDR) on the RX side. The TX PLL multiply the refere=
nce clock up and latch data out. In a lot serial links, data is 8B/10B enco=
ded to ensure enough transition edges for the CDR to recover the clock. In =
that sense, the clock is "embedded".
>
> The CDR on the RX side will try to figure out the right timing to sample =
data based on the data transition it was seeing. The CDR fundamentally is a=
nother PLL, the loop inside the CDR move the sampling edge back and forth t=
o have it centered around the center of the data eye, thus recovering or "d=
e-embeding" the clock and use the recovered clock to latch in data.
>
> Wei
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx on behalf of Zhangkun
> Sent: Tue 4/4/2006 8:51 PM
> To: si-list
> Subject: [SI-LIST] How to embedded and to deembedded the clock to serial =
signal, such as GE and PCI-E
>
> Dear all
> Recently, in our product, there is some problem in our product. The seria=
l signal, such as GE and PCI-E, has error bits. We have found out the reaso=
n:
>    1.The serial signal has crosstalk.
>    2.The clock signal to PLL has crosstalk.
>    3.The analog power of the PLL or the serial signal driver has large po=
wer noise.
>
> I guess the basic reason is that the jitter of clock. Could anybody expla=
in to me how the clock signal is embedded to and deembedded from the serial=
 signal?
>
> Best Regards
>
> Zhangkun
> 2006.4.5
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