On 01/07/2011 12:42 AM, Gerhard Hoffmann wrote:
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.
But one has to recall that a 0->1 transition can occur between the
words, and one also has to recall to identify the first 0->1 transition
in such a word with a bit-number indication.
Also, one has to count the number of 0->1 transitions in each word, such
that the event counter can be accumulated with the contribution from
each word.
A convenient approach is to use a tree structure to summaries and
identify things hierarchically. The last bit of the previous word needs
to be known.
For a 16-bit word, 16 rise detections is needed, and 15 early/late
comparators & summers is needed. This architecture can be suitably
pipe-lined to maintain full speed.
If one wants falling detections as well, then just invert the samples or
let the rise-detections also do fall-detection. Goes into one LUT
regardless (three-inputs rather than two inputs).
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
