[time-nuts] No State Of The Art Counter
magnus at rubidium.dyndns.org
Thu Jan 6 23:24:31 UTC 2011
On 01/06/2011 11:54 PM, Gerhard Hoffmann wrote:
> Am 06.01.2011 22:45, schrieb Gerhard Hoffmann:
>> I was thinking about abusing the built-in SERDES-Units in the Spartan6
>> as a prescaler. It would
>> be necessary to sort out the transitions after the 1:16 gearbox, but
>> given the amount of logic in a Spartan6
>> that should be possible. While I have not seriously tried that, I have
>> spotted no show stopper
>> in the data sheet.
>> The SERDES units are used for PCI-express, USB3 or fiber optic links
>> It should be possible to reach 3 or 4 GHz.
> To clarify this:
> That would not be a prescaler but a full range extension.
> Timestamping would be possible at 3 or 4 GHz.
> And I meant SATA-3, not USB3.
For a SERDES to be useable as a high frequency input, the Rx SERDES
needs to be able to use the reference clock as clock source rather than
doing clock recovery. While the SERDESes I have seen is able to do that,
one always want to check that detail before going further into the
design. For reference you typically use a SAW-oscillator which in this
case probably should have a VC input so you can lock it up. Should not
be too hard to find a suitable one.
I've considered this approach myself, but just not got around to cook
It's a bit of a design-challenge to do a parallel trigger detection and
event counter, but it is doable.
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