Meinberg UA509P, Руководство по эксплуатации

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signal. If the antenna is installed properly and the signal from DCF77 can be received
without strong distortions, the "Mod." LED starts blinking exactly once per second,
corresponding to the time marks from DCF77. If this LED flashes intermediately,
there is some electrical noise around which prevents the microprocessor from deco-
ding the time message. So a better location for the antenna must be found. In case of
correct reception it takes up to three minutes after power-up until the clock is
synchronized and the "Freil." LED is turned off. It is turned on again to indicate the
loss of or an error in reception. Without RF signal the clock runs on XTAL with an
accuracy of 10
-6
. If the clock have lost reception for more than 12 hours the "Freil."
LED starts blinking.
The serial outputs are enabled immediately after power up. Baudrate, framing,
output mode and time zone can be configured separately by two DIL switches.
LF Receiver
An external ferrit antenna is used to receive the signal from DCF77 and supplies it to
the on-board LF receiver where it is demodulated by a synchronous detector with
automatic gain control. The demodulated time marks are fed to the clock´s micropro-
cessor.
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. A
flash EPROM is used as program memory which can be loaded with the firmware by
the serial interface COM0.
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.