Garmin HVS GPS17 Technical Specifications page 21

The highly accurate one-pulse-per-second (PPS) output is provided for applications requiring precise timing
measurements. After the initial position fix has been calculated, the PPS signal is generated and continues until the
unit is powered down. The rising edge of the signal is aligned to the start of each GPS second within 1 μs for all
conditions in which the receiver has reported a valid and accurate position for at least the previous 4 seconds.
The NMEA 0183 sentences that follow each rising edge of the PPS signal tell when you were and where you were at
that previous rising edge of the PPS signal, beginning with the GPRMC sentence as the lead sentence in any
particular NMEA 0183 record.
Regardless of the selected baud rate, the information transmitted by the GPS 17x HVS is referenced to the pulse
immediately preceding the NMEA 0183 RMC sentence.
The accuracy of the one-pulse-per-second output is maintained only while the GPS receiver is computing a valid
position fix. To obtain the most accurate results, the one-pulse-per-second output should be calibrated against a local
time reference to compensate for cable and internal receiver delays and the local time bias.
The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms and 980 ms
as described in PGRMC section 4.1.2 Sensor Initialization Information (PGRMI), field <13>.
190-00885-07 GPS 17x HVS Technical Specifications Rev. A
Page 17