[SI-LIST] DDR2 Controller Receiver DQS Delay Chain Measurement.
- From: "rajeev sharma" <rajeev_ymca@xxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: 13 May 2008 10:01:45 -0000
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.
Is any such kind of solution available?
Thanks & Regards,
Rajeev
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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