Meinberg PZF511 - Manual (Page 16)

16
Asynchronous serial interfaces
Three independant serial RS232 interfaces are available at the rear connector of the clock
PZF511. As set in menu SER.MODE, the serial ports can send the a time string either
per second, per minute or on request by sending an ASCII '?' (3F hex) to the clock.
Additional menus are used to set the framing and baudrate of these interfaces as well as
the format of the time string. The structure of the strings are described in the chapter
"Time Strings".
Pulse outputs
TTL-low and TTL-high active pulses per minute and per second are generated by the
PZF511, which are available at the VG-connector. TTL-high active pulses per 15
minutes (P_15MIN) are also 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 PZF511 provides four standard frequencies. The outputs 100kHz, 155kHz, 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.