Protocol decoder:Dcf77

dcf77

Name	DCF77 time protocol
Description	European longwave time signal (77.5kHz carrier signal)
Status	supported
License	GPLv2+
Source code	decoders/dcf77
Input	logic
Output	dcf77
Probes	DATA

The dcf77 protocol decoder supports the DCF77 european longwave time signal (77.5kHz carrier signal).

Hardware

DCF77 on the Pollin DCF1 module

The dcf77/pollin_dcf1_module directory in sigrok-dumps contains a set of example captures of a DCF77 signal. The hardware used for receiving the signal is a Pollin DCF1 module (3.3V supply). The Pollin order number for the module is 810 054.

The dumps were made January 9, 2012 in the evening/night. Only the dcf77_480s_pon_interrupted.sr dump was made January 10, 2012 in the evening.

The logic analyzer used was a Saleae Logic (at 1MHz).

Probe setup:

Probe	DCF1 module
1 (black)	PON
2 (brown)	DATA

Photos:

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Protocol

Time code interpretation (taken from Wikipedia)

The time is represented in binary-coded decimal (BCD). It represents civil time, including summer time adjustments. The time transmitted is the time of the following minute; e.g. during December 31 23:59, the transmitted time encodes January 1 00:00.

Bit	Weight		Meaning		Bit	Weight		Meaning		Bit	Weight		Meaning
	PM	AM				PM	AM				PM	AM
:00	1	M	Start of minute. Always 0.		:20	S		Start of encoded time. Always 1.		:40	10		Day of month (continued)
:01	1	Civil warning bits, provided by the Bundesamt für Bevölkerungsschutz und Katastrophenwarnung (Federal Office of Civil protection and Disaster Relief). Also contains weather broadcasts.			:21	1		Minutes 00–59		:41	20
:02	1				:22	2				:42	1		Day of week Monday=1, Sunday=7
:03	1				:23	4				:43	2
:04	1				:24	8				:44	4
:05	1				:25	10				:45	1		Month number 01–12
:06	1				:26	20				:46	2
:07	1				:27	40				:47	4
:08	1				:28	P1		Even parity over minute bits 21–28.		:48	8
:09	1				:29	1		Hours 0–23		:49	10
:10	0				:30	2				:50	1		Year within century 00–99
:11	0				:31	4				:51	2
:12	0				:32	8				:52	4
:13	0				:33	10				:53	8
:14	0				:34	20				:54	10
:15	R		Call bit: abnormal transmitter operation. Previously: backup antenna in use.		:35	P2		Even parity over hour bits 29–35.		:55	20
:16	A1		Summer time announcement. Set during hour before change.		:36	1		Day of month. 01–31		:56	40
:17	Z1		Set to 1 when CEST is in effect.		:37	2				:57	80
:18	Z2		Set to 1 when CET is in effect.		:38	4				:58	P3		Even parity over date bits 36–58.
:19	A2		Leap second announcement. Set during hour before leap second.		:39	8				:59	0	Minute mark: no amplitude modulation.

Resources

• Wikipedia: DCF77
• PTB: DCF77 (German)