Appendix B - Serial Interface Specifications
B-2
560-0982-01 Rev A
GNS 480 (CNX80) Installation Manual
B.1.1 Altitude Encoder/Converter Input
The GNS 480 will accept various serial altitude formats. The only configuration required for the altitude
encoder input is the baud rate – the serial altitude format will be recognized automatically. The input
signals shall be compatible with RS-232C and have the following characteristics:
Baud rate: ...............................................1200/9600 (defined by encoder used)
Data bits: ................................................8
Stop bits: ................................................1
Parity: .....................................................none
Expected input rate: ...............................approx. 1 second
Message length: ......................................17 characters
B.1.1.1 Apollo Altitude Format
The Apollo (IImorrow) altitude format is 1200 baud with a message length of 17 characters, as defined in
Table B- 2. Several sample messages are illustrated in Figure B- 1.
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.
Summary of Contents for GNS 480
Page 1: ...GNS 480 CNX80 Color GPS Nav Com Installation Manual September 2004 560 0982 01 Rev A...
Page 10: ...Table of Contents viii 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 30: ...General Information 1 20 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 126: ...Periodic Maintenance 6 2 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 150: ...Appendix D Interconnect Diagrams D 2 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
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