Trimble Outdoors SPSX51 - Manual (Page 178)

I Receiver Connector Pinout Information
176 SPSx51 Modular GPS Receivers User Guide
1PPS and ASCII time tag
The SPSx51 receiver can output a 1 pulse-per-second (1PPS) time strobe and an
associated time tag message. The time tags are output on a user-selected port.
The leading edge of the pulse coincides with the beginning of each UTC second. The
pulse is driven between nominal levels of 0.0 V and 5.0 V (see
Figure I.1 ). The leading
edge is positive (rising from 0 V to 5 V).
Figure I.1 Time tag relation to 1PPS wave form
The pulse is about 8 microseconds wide, with rise and fall times of about 100 nsec.
Resolution is approximately 40 nsec, but the following external factor limits accuracy
to approximately ±1 microsecond:
• Antenna cable length
Each meter of cable adds a delay of about 2 nsec to satellite signals, and a
corresponding delay in the 1PPS pulse.
1PPS is available on pin 20 on the back connector of the receiver. If you have
applications that require 1PPS, Trimble recommends that you use cable P/N 60789-00
because it has the following connectors:
• D9 port for modem 1/serial 2.
• D9 port for modem 2/serial 3. Pin 9 on this D9 port has 1PPS.
• BNC connector for 1PPS.
• Ethernet male plug for connection to receiver.
• USB plug.
• DC jack for supplying power to the receiver.
Positive slope pulse
Time tag applies here
Time tag output here
Seconds
0 V
5 V