Meinberg PZF510 - Manual (Page 13)

13
Asynchronous serial interfaces
Two independant serial interfaces (RS232) are available at the rear connector of the
clock PZF510. As set in menu 'Ser. Mode', the serial ports can send the Meinberg
standard time string either per second, per minute or on request. Additional menus are
used to set the framing and baudrate of these interfaces. The time string is build of 32
ASCII characters and inlcudes information about time, date and status. The structure
of the string is described in chapter 'Format of the Meinberg stantard string'.
Pulse outputs
TTL-low and TTL-high active pulses per minute and per second are generated by the
PZF510, which are available at the VG-connector.
Because the internal time frame of the clock has not yet been synchronized with the
pseudo random sequence, no pulses are generated directly after reset. In case of
normal receiption, the receiver needs about 12 seconds for coarse and another 5
seconds for fine synchronization. So, pulses are generated approximately 17 seconds
after reset.
Standard frequencies
The PZF510 delivers six standard frequencies. The outputs 100kHz, 1MHz and 10MHz
are derived from the main oszillator of the clock which is phase locked to the DCF-
system by a digital PLL (phase locked loop). The temperature-dependant drift and the
aging of the oszillator can be compensated by this procedure. Therefore the excellent
short-term stability of the standard frequencies of +/- 5·10
-9 (standard version with
TCXO) is achieved. The value for regulating the digital-to-analog converter of the PLL
is avilable directly after reset because it is stored in the battery-backed RAM of the clock.
If the DCF-transmitter fails, the oszillator is controled by this value also. The accuracy of
the standard frequencies will not be worse than 1·10
-8 for one hour without receition
therefore.
The outputs 77.5kHz, 155kHz and 310kHz are locked to the receiver-PLL directly.
They are derived from a DDS-circuit (DDS: direct digital synthesis) which causes a
high phase jitter compared to the other standard frequencies. These outputs should
only be used as standard frequencies if the receiver is synchronous with DCF77.