RE: [SI-LIST] : tracking/oversampling PLL architectures

About this list Date view Thread view Subject view Author view

From: Keith Amundsen (kamundsen@cportcorp.com)
Date: Mon Mar 13 2000 - 12:01:08 PST


A Digital Phase Locked Loop (DPLL) is the oversampling variety. They may
have a tracking mode and a hold mode. In the tracking mode a special or
preamble pattern with maximum transition density is covenant to quickly
determine the bit centers for sampling. Then in the hold mode during random
data, the DPLL is not allowed to adjust anywhere near as often. Polynomial
scrambling circuits, turned on at the data source after the preamble ends,
etc., can be used to help ensure transitions during hold mode.
Regards, Keith

-----Original Message-----
From: Ooi, Thien Ern [mailto:thien.ern.ooi@intel.com]
Sent: Friday, March 10, 2000 8:29 PM
To: 'si-list@silab.eng.sun.com'
Subject: RE: [SI-LIST] : tracking/oversampling PLL architectures

Once the appropriate sample has been determined, how frequently does the
sample choice need to be updated? Is a special data pattern needed to
update the sample choice, or random data will do, as long as there is a
certain minimum transistion density?

-----Original Message-----
From: david_instone@uk.xyratex.com [mailto:david_instone@uk.xyratex.com]
Sent: Thursday, March 09, 2000 1:56 AM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : tracking/oversampling PLL architectures

<snipped>

In the oversampling PLL, which technically isn't a pll, a local and
relativly stable clock is used to sample the incoming bitstream several
times during each bit period. Logic then determines on a bit by bit
basis which of the several samples is the one to be used. You don't
actually have to have a local clock that is many times the frequency of
the bit rate, just generate several phases of a clock at the bit rate.

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list
or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:35:34 PDT