Meinberg GPS169PCI - Manual (Page 10)

10
DCF77 emulation
The GPS169PCI satellite clock generates TTL level time marks (active HIGH) which
are compatible with the time marks spread by the German long wave transmitter
DCF77. This long wave transmitter installed in Mainflingen near Frankfurt/Germany
transmits the reference time of the Federal Republic of Germany: time of day, date of
month and day of week in BCD coded second pulses. Once every minute the complete
time information is transmitted. However, the clock generates time marks representing
its local time as configured by the user, including announcement of changes in daylight
saving and announcement of leap seconds. The coding sheme is given below:
Time marks start at the beginning of a new second. If a binary "0" is to be transmitted,
the length of the corresponding time mark is 100 msec, if a binary "1" is transmitted,
the time mark has a length of 200 msec. The information on the current date and time
as well as some parity and status bits can be decoded from the time marks of the 15th
up to the 58th second every minute. The absence of any time mark at the 59th second of
a minute signals that a new minute will begin with the next time mark. The DCF
emulation output is enabled immediately after power-up.