[time-nuts] No State Of The Art Counter

[Gerhard Hoffmann]

Am 07.01.2011 00:24, schrieb Magnus Danielson:
>
> 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.
>
On The SP605 board, you can inject the clock via 1 or 2 SMAs, single 
ended or differential

> I've considered this approach myself, but just not got around to cook 
> something up.
>
> It's a bit of a design-challenge to do a parallel trigger detection 
> and event counter, but it is doable.

Yes.
If you look at the input signal as a 4 GB/s bit stream, you get it 
served as a 16 or 32 bit wide stream
at 1/16 or 1/32 the rate. Recognizing the 0->1 and 1->0 transitions may 
need some pipeline stages
and some work, but it is not really difficult.
The time stamp is simply the serial number of the 16/32 bit word and the 
location of the bit that flips.

Plowing with the power of a thousand chicken.

Gerhard    :-)