Real-Time Clock Patch For Dcf77 On The Commodore C64

36 EE July/August 1988 REAL-TIME CLOCK PATCH FOR DCF77 ON THE COMMODORE C64 An experimental interrupt routine is discussed that enables the Commodore C64 home computer to display time and date information received from time standard service DCF77. The publication in this magazine of a re- ceiver, intelligent time standard, and locked frequency reference based on Federal Germany"s time signal trans- mitter DCF77 (References 1. and 2.) has been a great success. Usable reception for synchronizing the microprocessor- driven clock in the intelligent time stan- dard has been reported by numerous constructors in the UK, Ireland and Europe. Long-distance reception with synchronization taking place up to 10 times a day was reported from as far as Saudi-Arabia and central Sweden. Clearly, the Deutsche Bundespost has re- mained on the safe side when claiming that the transmitter"s normal range is about 800 kilometres. The DCF77 receiver and locked fre- quency standard was designed to operate...