[time-nuts] Strange DCF77 master clock data
celephicus at gmail.com
Sun Dec 9 10:28:08 UTC 2012
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.
Tom Harris <celephicus at gmail.com>
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