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Multi-Source Function System 7001RC - V02.01
hopf
Elektronik GmbH
Nottebohmstr. 41 • D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: [email protected]
3.2 DCF77 Signal
The DCF77 radio controlled clocks receive the time signal from a long wave transmitter in
Frankfurt/Main (Germany).
The DCF77 Signal transmits the central European time (CET) or the central European
summer time (CEST). This time will be calculated by the UTC time plus one hour (CET)
resp. two hours (CEST).
The DCF77 signal contains the complete time information (minute, hour, day of the week
and date). Sending by default:
•
in local time
•
with the actual time zone (St or WT)
•
with announcement bit for ST/WT change over
•
with announcement bit for leap second
The difference time, local time to UTC must be known by the receiver. In CET area the
difference time is +1 hour east direction. The system 7001RC calculates the exact UTC time
of the local time from the set difference time.
3.2.1 Structure of the Data String DCF77 Signal
Every second of a minute a particular time information is transmitted, except for the 59
th
second. The missing signal in this second indicates an imminent minute change in the next
second.
At the beginning of every second a pulse is put out for 100 or 200ms. The initial edge of the
pulse marks the exact beginning of the second.
The duration of the second markers of 100 and 200 ms (binary 0 and 1) are transformed into
a BCD-Code to decode the transmitted data string.
The time data string is divided into 3 different groups, each followed by a parity check:
•
P1 = number of minutes
•
P2 = number of hours
•
P3 = current day of the year , the day of the week and the year
The binary ones of a group are determined and increased to an even number by the parity
bit.
When a valid time information (CEST) is transmitted the 17
th
second marker takes 200ms.
One hour before the changeovers from CEST to CET or vice versa the 16
th
second marker
takes 200ms.
The coding is shown below:
