[time-nuts] Strange DCF77 master clock data

[Tom Harris]

That's the funny thing, the parity bit is correct for the value of DOW,
just that the DOW value is wrong.

On 9 December 2012 23:27, Azelio Boriani <azelio.boriani at screen.it> wrote:

> Is the parity bit P3 consistent? It protects the day of the month and that
> of the week.
>
> On Sun, Dec 9, 2012 at 1:24 PM, mike cook <mc235960 at gmail.com> wrote:
>
> > Le 09/12/2012 11:28, Tom Harris a écrit :
> >
> >  Greetings Time Nuts.
> >>
> >> Time related, but unusually so:
> >>
> >> I am examining the DCF77 (see http://en.wikipedia.org/wiki/DCF77 for a
> >> refresher) data output from a master clock intended to drive a series of
> >> slave clocks operated from 24V DC, interrupted by 100ms or 200ms pulses
> to
> >> signal '0'& '1' on the data. What I am seeing is that the "day of week"
> >> bits 42 through 44 inclusive do not code the day correctly, they seems
> to
> >> have a variable offset from the actual day, I have seen an offset from
> +1
> >> to +3. The rest of the data, ncluding parity bits, are OK. Today,
> >> 9/12/2012, the day is Sunday, which should be coded as '7'. However I am
> >> seeing a value of '3', which is Wednesday.
> >> Is this normal, do wired DCF77 slave clocks transmit munged dow data to
> >> prevent them being used with someone else's master clock? If they do I
> am
> >> hosed since I am trying to reverse engineer the master clock.
> >>
> >>    Is it just bit 44 being stuck on zero? or can each dow get varying
> > values?
> >
> > --
> > Les chiens aboient, et la caravane passe.
> >
> >
> >
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-- 

Tom Harris <celephicus at gmail.com>