Meinberg DCF77 UA509 - Manual (Page 7)

7
LF Receiver
An external ferrit antenna is used to receive the signal from DCF77 and supplies it to
the on-board direct conversion quadrature receiver with automatic gain control. The
demodulated time marks are fed to the clock´s microprocessor.
Microprocessor System
The time marks from the receiver circuit are filtered and decoded by the microproces-
sor system. Parity and consistency checks over a period of two minutes take care for
detecting errors in the received time telegram. The checked and decoded time is
written to the on-board real time clock and spread by the interfaces. A software
watchdog lets the microprocessor recover from malfunction. A power-fail comparator
resets the microprocessor if the supply voltage drops below a specified threshold.
Aflash EPROM is used as program memory which can be loaded with the firmware by
the serial interface COM0.
Display
An 8-digit LED display with 2.5mm character height shows the time or date of the
UA509. A switch in the front panel lets the user select to view either date or time. The
displayed time zone corresponds to the time zone assigned to the serial port COM0 by
a DIL switch.
Buffered Real Time Clock
In case of supply voltage failure the on-board real time clock keeps the time powered
by a backup capacitor for more than 150 hours. This capacitor does not need any
maintenance. Alternatively, the clock can be ordered with a lithium battery which has
a live time of at least 10 years guaranteed.
Pulse Outputs
The UA509 generates active high and active low pulses per second and per minute.
This TTL pulses are 200ms of lenght and valid immediately after reset.