Garmin GNC 420, Installation Manual, Page: 93 / 136

400 SERIES INSTALLATION MANUAL Page D-1
190-00140-02 Rev Q
Appendix D. 400 SERIES RS-232 FUEL/AIR DATA INPUT FORMAT
D.1 ELECTRICAL INTERFACE
The input signals shall be compatible with RS-232C. Data shall be input at 9600 baud with a word length
of 8 bits, one stop bit, and no parity. One message is received per second.
D.2 SHADIN ALTITUDE SENTENCE
The Garmin 400 Series units shall be capable of receiving the following 17-byte message from Shadin
Altitude Encoders, Altitude Serializers, and Altitude Converters:
RMS<sp><+/->12345T<+/->12ul<CR>
Where:
RMS ASCII characters
<sp> space (0x20)
<+/-> sign indicator (0x2b["+"] or 0x2d["-"])
12345 altitude in feet
T ASCII character
<+/-> sign indicator
12 sensor temperature
ul checksum of bytes 1 through 14 in hex ASCII (i.e., "FA")
<CR> carriage return (0x0d)
Note: Checksum is calculated by adding each byte in the message (1 through 14).
D.3 ICARUS ALTITUDE SENTENCE
The Garmin 400 Series units shall be capable of receiving the following 10-byte message from the Icarus
Altitude Serializer:
ALT<sp>12345<CR>
Where:
ALT ASCII characters
<sp> space (0x20)
12345 altitude in feet
<CR> carriage return (0x0d)