Garmin GNS 480 Installation Manual page 131

B.1.1.2 Shadin Altitude Format
The Shadin altitude format is 9600 baud with a message length of 17 characters, as defined below:
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
sensor temperature
12
checksum of bytes 1 through 14 in hex ASCII (e.g., "FA")
ul
<CR> carriage return (0x0d)
Note: Checksum is calculated by adding each byte in the message (1 through 14).
GNS 480 (CNX80) Installation Manual 560-0982-01 Rev A
Figure B- 1 - Altitude Data Input
Appendix B - Serial Interface Specifications
B-3