[SI-LIST] Re: Will ODT on DDR2 work?

Jeff & all, 

Thanks for help to you and to other people who responded, but I have one
more question. You say "Yes of course ODT is enabled only on receive at the
Micron", but I think that on Virtex-5 they have DCI which can also be used
for terminating bidirectional lines. Why would you see problem with using
DCI? My main interest is to free-up our extremely congested real estate area
- it looks worst that Manhattan at 5:30 PM - and also I am hoping to get
better SI performance, since resistors will be closer to receivers.

Sorry troubling, but I do not want to discover that digital guys cannot
terminate my line for some reason.

Ludvik

+++++++++++++++++

> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Jory McKinley
> Sent: Tuesday, February 06, 2007 11:39 AM
> To: jeffjohnson@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Will ODT on DDR2 work?
> 
> Jeff,
> Yes of course ODT is enabled only on receive at the
> Micron.  I think the point here is that can we get
> away without using any on board resistors by taking
> advantage of the ODT that the Micron part provides.
> Why? probably not for the 30 cent or so savings (you
> never know) but more than likely the space required to
> place resistors for all the Data, Strobe, DM traces.
> -Jory
> 
> 
> --- Jeff Johnson <jeffjohnson@xxxxxxxxxxxx> wrote:
> 
> > Jory, Ludvik,
> >
> > Remember that ODT only works when the I/O is in the
> > "I" state.  I do not
> > recommend saving 30 cents of resistors for the
> > trouble-shooting headache you
> > will create.  Refer to JESD79-2C for more
> > information on how DDR2 works.
> >
> >
> > Date: Mon, 5 Feb 2007 18:14:57 -0800 (PST)
> > From: Jory McKinley <jory_mckinley@xxxxxxxxx>
> >
> > Subject: [SI-LIST] Re: Will ODT on DDR2 work?
> >
> > Hello Ludvik,
> >
> > In my experience it always a good idea to simulate
> > this transfer but we have
> > found that using Full ODT drivers on the Micron side
> > tend to create some
> > undesirable Signal Integrity issues at the
> > Controller (in your case the
> > Virtex-V). In most cases a Half strength ODT driver
> > will work however you
> > will need to simulate this while checking for
> > overshot and ringback at the
> > Virtex-V. Also make sure that you have adequate
> > crosstalk rules in place.
> >
> > -Jory
> >
> > Jeffrey Johnson, C.I.D.
> >
> > Module R&D Engineer
> >
> > NanYa Technologies - Texas LLC
> >
> > Tel: (713) 774-4113 Ext. 135
> >
> > FAX:  (713) 774-3819
> >
> >  Share your knowledge. It's a way to achieve
> > immortality.
> >
> >
> >
> >
> >
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> 
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