Garmin Apollo CNX80, Installation Manual

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Appendix B - Serial Interface Specifications
B-2 560-0982-00 Rev D Apollo CNX80 Installation Manual
Table B- 2 - Altitude Input Data
Byte Data Format Description
1 “#” ASCII “#” (023h)
2 “A” ASCII “A” (041h)
3 “L” ASCII “L” (04Ch)
4 “ “ ASCII space (020h)
5 “+” or “-” Altitude sign: ASCII “+” or “-” (02Bh or 02Dh)
6-10 ddddd Altitude in feet, right justified with leading zeros
11 “T” ASCII “T” (054h)
12 “+” or “-” Temperature sign: ASCII “+” or “-” (02Bh or 02Dh)
13-14 dd Internal altimeter temperature
15-16 dd Checksum of bytes 1 through 14, computed in hex, output in ASCII
format (i.e., “FA” hex)
17 <CR> ASCII carriage return (0Dh)
The altitude input can decode several status or error codes. These codes would be in place of the altitude
data in characters 5 - 10 as follows.
“-09980”................................................Heater not ready: expected during encoder warm-up or if
there is a loss of signal from the encoder.
“-09981”................................................Possible hardware problem: expected from encoder
indicating a temperature greater than 55
°
C or if data is
invalid.
“-09982”...............................................Altitude out of range: expected from the encoder
indicating that the altitude is outside specified range of
the encoder.
Figure B- 1 - Altitude Data Input