Moog Crossbow NAV440 Series - Manual (Page 38)

Page 38
NAV440 User Manual
7430‐0131‐01 Rev. F
1 PPS Input Interface
The 1PPS input signal allows the user of the 440 Series unit to force synchronization of sensor data collection to a
1Hz rising‐edge signal. The signal must maintain 0.0‐0.2 V zero logic and 3.0‐5.0 volts high logic and stay within
100ms of the internal system 1 second timing. Sending this signal to the system will align the sensor data collection
and algorithm processing to its rising edge and 10ms boundaries thereafter. When the system is synchronized to
1PPS, the hardwareStatusÆunlocked1PPS flag will be
; otherwise, the flag will be . zero one
1 PPS Output Interface
The 1PPS output signal is provided by the internal GPS receiver (when GPS timing is known) on the 440 Series unit.
The 1PPS output signal is open‐collector and should be interfaced to a rising‐edge trigger with pull up resistor
between 1k and 10k ohms. The 440 Series unit 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 1PPS.
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 440 units, then the
rising ed
hardware Status
ge of 1PPS will correspond to the UTC second boundary. When the system is synchronized to 1PPS, the
Æ unlocked1PPS flag will be zero; otherwise, the flag will be one.
igure 6 F
t
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.
Figure 6 1PPS Output Signal