Garmin GNC 255 Installation Manual - page 81
190-01182-02
GTR 225/GNC 255 TSO Installation Manual
Rev. B
Page B-1
APPENDIX B GTR/GNC DATA FORMAT
B.1
RS-232 Aviation Data Format
B.1.1 Electrical Interface
The I/O signals are compatible with RS-232C. Data is generated at 9600 baud with a word length of 8 bits,
one stop bit, and no parity.
B.1.2 General Aviation Output Format
The GTR/GNC RS-232 data has the following general format:
STX
- ASCII start-of-text character (02 hex)
t1s
- Type 1 output sentences (see following paragraphs for description)
t2s
- One or more type 2 output sentences (see following paragraphs for description)
ETX
- ASCII end-of-text character (03 hex)
B.1.3 Aviation Output Sentence Type 1
The Type 1 output sentences have the following general format:
id
- item designator (single ASCII alphabetic character)
dddd
- item data (1 to 10 printable ASCII characters)
CR
- ASCII carriage return character (0D hex)
LF
- ASCII line feed character (0A hex)*
Each Type 1 sentence is output by the GTR/GNC approximately once every second.
The track, desired track, and bearing to waypoint angles, and the magnetic variation are output according
to the current mode of the GTR/GNC (automatic magnetic heading, magnetic variation computed at last
known position; true heading, magnetic variation of E00.0°; or user-defined magnetic heading, magnetic
variation as entered by user).
Table B-1 describes the Type 1 output sentence item designator (id) and item data (dddd) fields. If data for
these sentences is invalid or unavailable, dashes ("-") are used to fill in all non-blank character positions.