[SI-LIST] Re: DDR3 routing Topology selection

  • From: Ramesh Natesh <rameshnatesh@xxxxxxxxx>
  • To: vinod.kumar@xxxxxxxxxxxx
  • Date: Tue, 25 Jun 2013 12:33:34 +0530

The length matching requirement depends on the DDR PHY's (on the processor)
ability to level the lane delay skews. The delay lines in the PHY have a
max. limit and the lane-to-lane skew requirement is borne out of this limit.
To answer your question:
a) It is NOT important to length match CK with DQ/DQS. Write leveling
compensates for the skews (again, within the max. limit)
b) As I mentioned above, you need to conform to the length matching
requirements laid out by processor.

-regards,
Ramesh


On Tue, Jun 25, 2013 at 12:14 PM, Vinod Kumar <vinod.kumar@xxxxxxxxxxxx>wrote:

> One more question
>
> Whether we are using T or Fly by, how important it is to length match
> data/strobe signals with clock signal?
> General layout guidelines for all processors mention some length matching
> requirements, but is it really required?
>
> Regards,
> Vinod
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Sen Velmurugan
> Sent: Thursday, June 20, 2013 11:33 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: DDR3 routing Topology selection
>
> Vinod,
> You need to check the setup n hold time margin for the choice of topology
> before finalizing.
> Thanks
> Sen
>
> Msg: #12 in digest
> From: "Vinod Kumar"<vinod.kumar@xxxxxxxxxxxx>
> Subject: [SI-LIST] Re: DDR3 routing Topology selection
> Date: Wed, 19 Jun 2013 17:09:45 +0530
>
> Hi Hermann,
>
> Thank you very much for your inputs.
>
> And extra time for calibration is not an issue. My main concern is the
> support for DDR3 calibration with the BSP that I got from vendor.
> In the reference board, there are four DDR3 chips and T-topology is used
> and
> there are no terminations. So I am not sure if write leveling is supported
> in the reference code. I was actually thinking about those additional
> efforts if there is no code support. BTW, I am inclined more towards fly by
> topology.
>
> Regards,
> Vinod
>
>
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-- 
-best regards,
Ramesh Natesh
+91 9886284671
(rameshnatesh@xxxxxxxxx)


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