Moog Crossbow GNAV540 - Manual (Page 37)

GNAV540 User Manual
7430‐0808‐01 Rev. B Page 37
1 PPS Output Interface
The 1PPS output signal is provided by the internal GPS receiver (when GPS timing is known) on the GNAV540. The
1PPS output signal is open‐collector and should be interfaced to a rising‐edge trigger with pull up resistor between
.
S.
1k and 10k ohms. The GNAV540 synchronizes sensor data collection to this 1PPS signal internally when available
Therefore, the 100Hz navigation algorithm will run exactly 100 times each second with no slip when locked to 1PP
Packet data is valid on the rising edge of 1PPS and 10ms boundaries thereafter. There is, however, up to 500µs of
additional latency in sensor data collection. If 1PPS is provided by the internal GPS receiver in NAV products, then
the risin e
hardwareStatus
g edge of 1PPS will correspond to the UTC second boundary. When the system is synchronized to 1PPS, th
Æ unlocked1PPS flag will be zero; otherwise, the flag will be one.
Figure 5 below shows the sequential order of the signal present at 1 PPS OUT pin. The one PPS signal is aligned to
he sampling clock of 23.104 MHz, which results in the timing resolution of 43 ns. t
Figure 5 1PPS Output Signal