[SI-LIST] Re: DDR2 Controller Receiver DQS Delay Chain Measurement.

http://www.xilinx.com/products/design_resources/mem_corner/index.htm


> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of rajeev sharma
> Sent: Tuesday, May 13, 2008 3:02 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] DDR2 Controller Receiver DQS Delay Chain
Measurement.
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> Hi All,
> We have a DDR2 Controller and I want to characterize the DQS Delay
Chain,
> which is used to shift  the DQS(which is edge aligned to DQ data)
signal
> coming from the DDR2 memory.
> Using a DDR2 memory on my board  and communicating with my controller
> doesn't help much as the memory doesn't provide me an option to vary
the
> Skew between DQS and DQ from memory to study the DQs Delay Chain in my
> controller.
> Does someone has an Idea how to test this Delay Chain?Is there any
> solution available in the market?
> One way could be to get an FPGA with DDR2 memory functionality in it
and
> then plug this FPGA  on my Controller Board.The FPGA(working as DDR2
> memory) should provides the flexibility to vary the Skew between DQS
and
> DQ.
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> Is any such kind of solution  available?
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> Thanks & Regards,
> Rajeev
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> On Mon, 12 May 2008 mwilbur@xxxxxxxxxxxx wrote :
> >I've used spectre more than hspice, but typically transient sims
don't
> include
> >noise effects, so you won't get any jitter there.  With Cadence
tools,
> you have
> >to use ac noise, pnoise or a special time-domain noise option for
> transient
> >runs.
> >
> >As always, your simulations can be no more accurate than your models.
> So,
> >caveat emptor.
> >
> >Matt
> >
> >Quoting Andrew Ingraham <a.ingraham@xxxxxxxx>:
> >
> > > > The time period may differ from one cycle to the next in the
> > > > output, so i have to measure the period for every consecutive
cycle
> for
> > > > about 1000 cycles.the only way i got to know is using 1000
.measure
> > > > statements. however i wish to know if there is abetter way of
doing
> this?
> > >
> > > Read the waveforms into a SPICE plotting program and use its
> capabilities to
> > > find the zero-crossings.  You usually get far better manipulation
and
> > > analysis capabilities in plotting and post-processing programs
than
> with the
> > > SPICE engine itself.  I don't use HSpice's own graphing programs
so I
> don't
> > > know what they are capable of.
> > >
> > > However, it is questionable whether a SPICE run will show you all
the
> > > variations you will encounter, including noise, temperature
changes,
> etc.
> > > (unless you are clever enough to put these in to the run).  Some
of
> the 5%
> > > variation you talk about may be due to component tolerances,
> temperature,
> > > and voltage, which a single SPICE transient run won't show you.
> > >
> > > And in any event, many oscillators are not used during the first
> several
> > > hundred (or million) cycles after they are started anyway, so the
> start-up
> > > characteristics might not be interesting in reality.  If you were
to
> measure
> > > an actual oscillator with a scope or other instrument, you
probably
> wouldn't
> > > capture its waveform until a long time after it starts up.
> > >
> > > Andy
> > >
> > >
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