Garmin GNS 480, Installation Manaul, Page: 143 / 200

Appendix B - Serial Interface Specifications
GNS 480 (CNX80) Installation Manual 560-0982-01 Rev L
B.1.2.3 “PC-12” Data Format
The format of the fuel input is as follows, which conforms to the PILATUS PC-12 format serial message.
Definition of the input message data that the GNS 480 uses is included in Table B-45.
Baud rate: ............................................... 9600
Data bits: ................................................ 8
Stop bits: ................................................ 1
Parity: ..................................................... none
Expected input rate: ............................... approx. 1.6 second
Message length: ..................................... 13 bytes
The serial input message string is expected in the following format.
<STX><message><message> ... <message><message><ETX>
<STX> .................................................... ASCII “start of text” character (STX = 02h)
<message> .............................................. See the following table.
<ETX> .................................................... ASCII “end of text” character (ETX = 03h)
Table B-5. Fuel Data Message (PC-12 Format)
Item
Desig
Message
Format Message
Mnemonic Field
Width
(bytes)
Message Description
Start STX 1 Start of Transmission
Units d UNIT 1 Units
4BH = Kilograms
42H = Pound
Fuel
Quantity
Remaining
dddd FQ 4 Fuel Quantity Remaining
ASCII-coded decimal format, LSB first.
Example: A fuel remaining value of 432 would be sent as
“2340” (32H,33H,34H,30H)
Fuel
Quantity
Checksum
d FQCK 1 Fuel Quantity Checksum
Break each decimal value into its BCD representation. Using
BCD arithmetic, sum the 4 BCD values and convert the low-
order PCD digit to and ASCII coded numeric digit.
Example: Checksum for a value of 432 would be “9” (39H)
Fuel Flow dddd FF 4 Fuel Flow (units/hour)
ACSII-coded decimial format, LSB first. (Same as FQ)
Fuel Flow
Checksum
d FFCK 1 Fuel Flow Checksum
Sum of fuel flow bytes computed same as FQCK
End ETX 1 End of Transmission
Note: When for any reason any data is not available is shall be transmitted as dashes (2DH).