Garmin GTR 225 Installation Manual page 95

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.
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. B
CDI needle, represented as two encoded hex
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. An eight bit
value indicating the amount of deflection of the CDI needle, represented as
two encoded hex digits. 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. digits. 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)
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
Bit 8 (msb)
$PGRMV219<64?:<chksm><CR><LF>
1
digits. The CDI deflection is a
Reserved
Localizer detect (1 = using localizer)
2
FROM flag (1 = From)
TO flag (1 = To)
GSI superflag (1 = hidden)
GSI valid (1 = valid)
NAV superflag (1 = hidden)
NAV valid (1 = valid)
GTR 225/GNC 255 TSO Installation Manual
Page B-15