5.5 DCF77 Emulation
Page 7
PPO2:
DCF77 Simulation
A TTL level master frequency of 10 MHz is derived from the TCXO. By default, this frequency is available only
at the 5 pin contact strip of the board.
5.5 DCF77 Emulation
The satellite controlled 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 Mainingen
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 generates time marks representing its local time as congured by the user, including
announcement of changes in daylight saving and announcement of leap seconds. The coding sheme is given
below:
M
Start of Minute (0.1 s)
R
RF Transmission via secondary antenna
A1
Announcement of a change in daylight saving
Z1, Z2
Time zone identification
Z1, Z2 = 0, 1:
Daylight saving disabled
Z1, Z2 = 1, 0:
Daylight saving enabled
A2
Announcement of a leap second
S
Start of time code information
P1, P2, P3
Even parity bits
0
10
20
30
40
50
R
M
1
4
2
1
20
10
8
4
2
1
P
2
0
2
0
1
8
4
2
1
2
4
8
10
1
2
4
8
10
2
0
4
0
8
0
3
P
A1
Z1
Z2
A2
S
1
2
4
8
1
0
2
0
4
0
1
P
Minute
(reserved)
Hour
Day of Month
Day of Week
Year of the Century
Month of Year
Time marks start at the beginning of 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.
GPS170PCI
Date: 12th July 2012
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