System Description

SystemDescriptionandInstallationManualforRangeFinder ICD1000001
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8.4.11 ModeCInterrogationResponseMessages:Type0xA2
The Mode C Interrogation Response Message is transmitted from Range Finder in response to a Mode C (or
ModeCWhisperShou t)interrogationcommandmessage.
IftheRangeFinderisabletoperformtherequestedinterrogation,thenthismessagecontainsthedatastored
inmemoryfromthelastvalidrepliesto
interrogation.Theinterrogationresponsemessagewill varyinlength
dependentuponthenumberofresponsesfromtheinterrogation.Notethatamaximumof64targetscanbe
reported in a single message; if the numberof targets exceeds 64, multiple responsemessages will be sent.
Thenumberoftargetsbeing
reportedinamessageisinferredthroughthepayloadlength,whichisfollowed
bythedataforeachresponseasdefinedinTable868.
An overview of Mode C Interrogation Response Messages is shown in Table 867.Table 868 provides the
detailedmessagedefinition.Foranexampleof
theuseofthismessageseeTable869.
Table867ModeCInterrogationResponsePayloadStructureOverview
PayloadIndex MessageField Numberbytes
00 PressureAltitude 2
02 Range 2
Table868ModeCInterrogationResponseMessagePayloadStructureDetail
PressureAltitude
ByteOffset ByteName FieldDescription
00 ALT0 ALT0 ALT1 PressureAltitude
01 ALT1 0x80
0xFF
0xFF
0xFF
0x00
0x00
0x04
0x04
0x00
0xF3
0xF4
0xFF
0x00
0x01
0xF3
0xF4
AltitudeUnavailable
OutofRange
1200ft
100ft
0ft
100ft
126,700ft
OutofRange
Altitude
[ALT0MSB][ALT1LSB]:MSBissentfirst
Thedataissentinthefollowing2'scomplementformat:Sddddddddddddddd
Theaircraftbarometricaltitudeismeasuredinfeetwithreferencetoapressureof29.9213”Hg
(101325Pascals)forzerofeetindication.
Dataresolutionis100feet:lsb=100feet
0x8000(32,768)indicatesaltitudeunavailable