Meinberg GPS161 - Manual (Page 9)

9
Asynchronous serial ports
Two asynchronous serial interfaces (RS-232) called COM0 and COM1 are available to
the user. Transmission speeds, framings and the kind of the time string can be configured
separately. The serial ports are sending a time string either once per second, once per
minute or on request with ASCII ‘?’ only. Possible time strings are ‘Meinberg Standard’,
‘SAT’, ‘UNI Erlangen (NTP)’, ‘ABB-SPA’ or ‘NMEA (RMC)’, see the technical
specifications for details. Furthermore, the serial interface COM0 is used for communica-
tion with the monitor program. A possible firmware update is also done via this serial
channel.
Enabling of outputs
In the default mode of operation the pulse outputs and the serial interfaces are disabled
until the receiver has synchronized after power-up. However, with the help of GPS-
MON32 the system can be configured to enable those outputs immediately after power-
up. This option can be set for each group of signals (pulses and serial interfaces)
seperately.
Status outputs
The satellite receiver clock GPS161 provides two TTL-outputs (/FAIL and LOCK) for
handing-over the status of synchronization of timing and calculation of position to post-
connected systems. These outputs can be used for driving LEDs via an external resistor
(R
min
= 470
Ω).
/FAIL output
The ‘/FAIL’ output switches to TTL high level whenever the internal timing of the
receiver is synchronous to the GPS-system.
LOCK output
The ‘LOCK’ output switches to TTL high level if the receiver has acquired at least four
satellites and has computed its position after power-up. In normal operation the receiver
position is updated continuously as long as at least four satellites can be received. When
the receivers position is known and steady only, a single satellite needs to be received for
synchronization and generatation of output pulses.