[SI-LIST] Re: eye mask- DDR2 address/command

  • From: Hermann Ruckerbauer <Hermann.Ruckerbauer@xxxxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Tue, 25 Jun 2013 08:36:10 +0200


generating a single official eye-mask for a DDR2 source Sync interface
is difficult (impossible ?!?).
There are many parameters that are need to fulfilled on a cycle by cycle
basis and with different timing references.
I tried to explain this a bit in the  DDR3 Setup_Hold tutorial (valid
for DDR2 as well):

I usually measure the open data window (ODW) from last AC crossing to
first DC crossing and compare this to the required setup/hold times (so
i do not draw the required eye Mask, but i measure what my system provides).
Just one example why it is difficult to work with a simple eye mask:
If you draw the "mask" according to setup and hold times then you get a
mask that is smaller than the allowed tDIPW (data input pulse width).

If you have a simulator it most likely provides a method to do the check
on a cycle by cycle basis (what would be the correct way to do).
For ADS this check is available too, but as mentioned above I do use
this ODW measurement based on own Code. 


EKH - EyeKnowHow
Hermann Ruckerbauer
Itzlinger Strasse 21a
94469 Deggendorf
Tel.:   +49 (0)991 / 29 69 29 05
Mobile: +49 (0)176  / 787 787 77
Fax:    +49 (0)3212 / 121 9008

schrieb Balamanikandan K:
> Hi
> I would like to know whether any standard eye mask available for DDR2
> -address/command signals or not. Please clarify me.

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