Garmin GTR 225 Installation Manual page 93

B.2.4.2.6 CDI, VDI, and Related Flags
This message outputs the current values of the CDI, VDI, and their related flags.
Message format:
"V" ..........................Message class. This is a GNC NAV message.
"21".........................Message identifier.
cc.............................CDI deflection. An eight bit value indicating the amount of deflection of the
gg ............................VDI deflection. An eight bit value indicating the amount of deflection of the
ff..............................Flags. Eight bits for HNAV and VNAV related flags, represented as two
Example message:
This message indicates a full left CDI deflection (-100), a full up VDI deflection (100), both the GSI and
NAV flags/superflags are valid, TO flag set, FROM flag not set, using a localizer.
Notes:
[1] Encoded hex: each character consists of 4 bits of data placed in the low order nibble +30h. For
example, the 8-bit value 5Fh would be encoded as two characters with values of 35h and 3Fh,
which map to the ASCII characters "5" and "?", respectively.
[2] The TO and FROM flag can not both be 1, indicating that they are both valid. They can both be
zero, indicating that neither is valid. This situation will occur whenever the receiver determines
that it is within the "cone of confusion" directly over a VOR, or when no signal is being
received.
190-01182-02
Rev. F
CDI needle, represented as two encoded hex digits. [1] The CDI deflection is
a twos complement signed integer in the range of –120 to 120. –100 indicates
full left deflection, 0 indicates no deflection, and 100 indicates full right
deflection. +/-120 indicates max left/right deflection.
VDI needle, represented as two encoded hexcc CDI deflection. The CDI
deflection is a twos complement signed integer in the range of –120 to 120. –
100 indicates full deflection upwards, 0 indicates no deflection, and 100
indicates full deflection downwards. +/-120 indicates max up/down
deflection.
encoded hex digits.
Bit 1 (lsb)Reserved
Bit 2Localizer detect (1 = using localizer)
Bit 3 FROM flag (1 = From)[2]
Bit 4TO flag (1 = To)
Bit 5GSI superflag (1 = hidden)
Bit 6GSI valid (1 = valid)
Bit 7NAV superflag (1 = hidden)
Bit 8 (msb)NAV valid (1 = valid)
$PGRMV219<64?:<chksm><CR><LF>
GTR 225/GNC 255 TSO Installation Manual
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