In Europe the Physikalisch-Technische Bundesanstalt in Braunschweig provides a reference time generated by an atomic clock. It is transmitted as time reference signal called DCF77 which can be used to synchronize clocks both for public and private use. The 50 KW sender in Mainflingen near Frankfurt transmits in the long wave band at 77.5KHz which permits the signal to be received inside a radius of 2000 km. Every minute a complete time packet containing year, month, day, hour and minute is sent out.
In this Semester thesis a fully integrated DCF77 alarm clock was implemented. It works with a minimum of external circuitry and provides a comfortable menudriven user interface with a 2-by-20 character LCD. Eight different alarm times can be se. Alarm auto-repeat and a down-counting timer is also implemented. High effort was spent for low power consumption as this chip is to be used in a battery-operated device. Therefore the chip contains several mechanisms for activating the sleep mode and the selective power-down mode.
The chip was successfully implemented, produced and tested. A demonstration board with a complete user interface was built to demonstrate the clock.