SIEMENS S7-300 SIPLUS DCF 77 radio clock module


This module can be used to synchronize the real-time clock of the SIMATIC/SIPLUS S7-200, S7-300 and S7-400 automation systems with the official time of the DCF 77 time signal transmitter of the Physikalisch-Technische Bundesanstalt Braunschweig, Germany.

The time is received by means of a DCF receiver (antenna with electronics) which is connected via two digital inputs on the SIMATIC PLC and SIPLUS together with a software driver available


By means of the radio clock module SIPLUS DCF 77 the official time of day of the time signal transmitter DCF 77 can be read in SIPLUS S7-200, S7-300 and S7-400; thus the existing real-time clock can be synchronised.

The time signal transmitter DCF 77 is situated in Mainflingen near Frankfort on the Main, the signal can be received within a radius of 2,000 km.

DesignSIPLUS DCF 77 radio clock module

The module consists of an antenna with electronics, including supports for wall mounting and software function block

A suitable mounting location should be selected so that a metal building facade cannot interfere with the radio signal. The radio reception must be checked at the mounting location.


The module is connected to the automation system by means of a 4-core cable (shielded). 3 LEDs can be monitored through the transparent cover. They have the following functions:

  • Green LED: “24Vdc”: Power supply is connected
  • Center red LED “DCF data”: data transfer to the automation system
  • Outer red LED “sec”: second settings from atomic clock

The following data is provided:

  • Minute – hour – calendar day – weekday – month – year
  • Automatic daylight-saving adjustment

Technical specifications

Radio clock module SIPLUS DCF 77

Radio frequency

77.5 Hz

Power supply

24 V DC (20.4 to 28.8 DC)

Power consumption, typ.

50 mA

Dimensions (W x H x D)

75 mm x 125 mm1) x 75 mm

1) Additionally 25 mm (0.98 in) for heavy duty threaded joint and bending radius for cables