[SI-LIST] Re: source-termination and daisy chain question
- From: olaney@xxxxxxxx
- To: mark.woods@xxxxxxxxxx
- Date: Wed, 4 Jul 2007 16:25:06 -0700
You scroll all the way to the bottom and read the instructions.
On Wed, 4 Jul 2007 16:01:00 -0700 "Mark Woods" <mark.woods@xxxxxxxxxx>
writes:
> How do I unsubscribe?
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of olaney@xxxxxxxx
> Sent: Tuesday, July 03, 2007 12:06 PM
> To: olaney@xxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: source-termination and daisy chain question
>
> All very true. Consider also that if the trace is short compared to
> the
> risetime, you can live with no termination at all. That's how
> classic
> TTL design was usually done, and still applies if the scale is right
> for
> the speed. Of course, some logic families require a termination to
> create proper logic levels.
>
> Orin
>
> On Tue, 03 Jul 2007 07:45:00 -0700 Terry Fox <tfox@xxxxxxxxx>
> writes:
> > Han,
> >
> > The answer depends upon the type of signal..
> >
> > If you are distributing a daisy chain multi drop clock, you need
> > load
> > termination. Clocks must have a clean edge.
> >
> > If you are distributing address or data which simply needs to
> settle
> > prior
> > to the clock edge, source serial termination is fine.
> >
> > Data or address lines are only required to get to the
> appropriate
> >
> > voltage prior to the set up time.
> >
> > One corner case involves a "T" connection for SDRAM memory clock.
>
> > If
> > there are only two drops and the arms of the "T" are identical,
> > you can often use source serial termination. It is not the best,
> > but it
> > works. I would HIGHLY recommend simulating this configuration
> > prior to layout and again after layout.
> >
> > If I have some time later, I will do some simulations and send you
>
> > the link.
> >
> > TFox
> > tfox@xxxxxxxxx
> > www.siemc.com
> >
> >
> >
> > At 11:25 PM 7/2/2007, Han Li wrote:
> >
> > >Hi everyone,
> > > It seems a simple question,But I still have something i
> > >cannot completly understand.
> > > A daisy chain is often used in multidrop topology, which
> > need an
> > >end-termination. And, source-termination doesnot work properly in
> > >daisy chain,because the device in the middle of the chain would
> get
> > a
> > >plateau;using source-termination, all load should be at the end
> of
> > the
> > >line.
> > > So, in a design , i should figure out minimul distance
> > between,
> > >say two receivers. In other words, I should decide beyond what
> > distance
> > >between two
> > >receivers , source-termination should not be used, and this
> > topology
> > >can be named a daisy chain?
> > > Could anyone provide a deeper explanation? Thanks a lot!
> > >---- ------ -------
> > >Driver---------revceiver_1-----------------------receiver_2
> > >---- ------- --------
> > > |-------------distance---------|
> > >
> > >
> >
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