[time-nuts] ANFSCD - Synchronizing time in home video recorders

Azelio Boriani azelio.boriani at screen.it
Thu Feb 2 21:21:22 UTC 2012


OK for the PSOC example. At the moment I can try on a Spartan3 because I
already have a board with the OCXO. The Spartan3 has the so called DCM, a
digital clock generator that can multiply an input clock using its DDL
digital delay line.

On Thu, Feb 2, 2012 at 8:13 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> tvb at LeapSecond.com said:
> > I'm not sure how well a multi-level leap year algorithm relates
> Breseham's
> > algorithm. I tracked down his 1965 plotter article. There might be common
> > ground there.
>
> It's the same math as a DDS.
>
> If Breseham would land exactly on a grid point after N steps,  a DDS will
> have no long term drift.  That means the slope of the Breseham line is N/M
> where both N and M are integers.  For the intermediate steps, both Breseham
> and DDS come as close as possible: 1/2 grid spacing vs 1/2 clock period.
>
> We usually think of DDS as requiring M to be a power of 2 but you don't
> have
> to do it that way.  One obvious example is to make M a power of 10 by doing
> decimal adds rather than binary.  That should work well with a FPGA but I
> haven't done it yet.  If you start with 10 MHz, that will give you perfect
> hits on integer audio frequencies.
>
>
>
>
>
> --
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
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