System Description
SystemDescriptionandInstallationManualforRangeFinder ICD10000‐01
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8.4.10 ModeAInterrogationResponseMessages:Type0xA1
TheModeA Interrogation Response Message is transmitted fromRange Finder in responseto a Mode A (or
ModeAWhisper‐Shout)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
by the data for each response as defined in Table 8‐65.Payload length will be 4 times the number of
responses.
Table 8‐66 is an example message returned to the Host computer containing 4 responses from
a Mode A
Interrogation.
An overview of Mode A Interrogation Response Message is shown in Table 8‐64.Table 8‐65 provides the
detailedmessagedefinition.
Table8‐64ModeAInterrogationResponsePayloadStructureOverview
PayloadIndex MessageField Numberbytes
00 SquawkCode 2
02 Range 2
Table8‐65ModeAInterrogationResponseMessagePayloadStructureDetail
SquawkCode
ByteOffset ByteName FieldDescription
00 SQK0 SQK0 SQK1 SquawkCode
01 SQK1
0x02
0x02
0x0E
0x08
0x00
0x80
0x00
0x99
1000
1200
7000
4231
SquawkSetting(4096Code)
[SquawkMSB][SquawkLSB]
Squawkissentasanunsigned16bitinteger.TheMSBissentfirst.Avalidsquawkisastringoffour3‐
bit(octal)numbers.Each3‐bitnumbercantakethevalue0‐7decimal.Validsquawksare0000to7777.
Forexample,thesquawk4231wouldbeformattedas:
0000100010011001(0x08:0x99)
Thusthevalidhexadecimalrangeofsquawkis0x0000to0x0FFF