ashtech DG16 Reference Manual page 64

The DG16 has an optional feature that allows you to output raw data (also called
real-time data) through serial ports A, B, and C. Five different messages can be
output:
• MBN: Contains measurement data for each locked satellite using the
Ashtech Type 2 data structure.
• PBN: Contains position and velocity data.
• SNV: Contains satellite ephemeris data.
• SAL: Contains satellite almanac data in a proprietary format.
• MCA: Contains measurement data (same as MBN) for each locked
satellite using the Ashtech Type 3 data structure
All raw data messages are in binary format. The transmission protocol remains
the same: 8 data bits, 1 stop bit, and no parity bit. Any combination of messages
can be output through any of the serial ports, and the same messages can be
output through different ports at the same time. The output interval is determined
by the $PASHS,RCI command, and can be set to any rate between 0.05 and 999
seconds depending upon which option has been selected for the raw
measurement update rate (20, 10, 5, 2, or 1 Hz). For more information on the
structure and content for all the above messages, see Chapter 7, Raw Data
Commands.
Output interval setting for raw data messages is 1 seconds.
With the photogrammetry [E] option installed, the DG16 can measure and record
events with high accuracy. The input signal is transmitted at TTL levels with 10
KW impedance. In order to measure an event time, a trigger signal must be sent
to pin 27 on connector J301. This input can be driven with either a TTL signal or a
switch that grounds the pin. The photogrammetry feature allows the event time to
be output by using the $PASHS,NME,TTT command.
Enabling the TTT message causes the TTT NMEA message to output in
synchronization with either the rising or falling edge (selectable) of the triggering
44
DEFAULT SETTINGS
DG14 and DG16 Board & Sensor Reference Manual