Owner's manual

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Page38
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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
Æunlocked1PPSflagwillbe
zero;otherwise,theflagwillbeone.
igure6
F
t
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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
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