[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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