Technical information

12
Connectors and LEDs in the rear panel
The rear panel includes the antenna connector, three status LEDs, the BSL button,
and a 9 pin sub D connector (see figure below).
The LEDs let the user check for proper receiver
operation. The upper, red LED is on if the clock is
not synchronous to DCF77. This LED can only
change when the minute changes (seconds incre-
ment from 59 to 0). The brightness of the LED in
the middle depends on the strength of the RF si-
gnal. The lower, green LED should be blinking
exactly once per second corresponding to the time
marks from DCF77. If this LED flickers there is
some electrical noise around which prevents the
receiver from decoding the time marks and syn-
chronizing. All information given by these LEDs is
also available via the monitor program.
The BSL button behind the hole in the slot cover
activates the clock's boot strap loader. This mode
of operation is needed if the clock's firmware shall
be updated.
The 9 pin sub D connector is wired to the radio
clock's serial port. Pin assignment can be seen
from the figure beside. This port can not be used as
serial port for the computer. Instead, the clock uses
the port to send out Meinberg's standard time
string in order to control an external display or
some other external device. The string is sent out
once per second, once per minute or if requested by
an incoming ASCII „?“. It is also possible to chan-
ge the radio clock's board time by sending such a
string towards the clock.
Transmission speed, framing, and mode of ope-
ration can be modified using the monitor program.
The string format is described in the section „Tech-
nical Specifications“ at the end of this manual.
antenna
free run
field strength
modulation
BSL key
RxD
TxD
GND