Garmin Apollo CNX80, Installation Manual

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Appendix B - Serial Interface Specifications
Apollo CNX80 Installation Manual 560-0982-00 Rev D B-11
B.2.1.4 NavComm Data
The definition of the NavComm portion of the MapCom data output is as follows. This data output is
compatible with the SL30 or SL40 for sending frequency data to the comm or nav unit.
The comm data is output using the following format.
$PMRRC<msg_id><msg_data><chksum><cr>
$PMRRV<msg_id><msg_data><chksum><cr>
The checksum is computed by an 8 bit addition of the msg_id and msg_data characters, ignoring carry if
any. The resulting 8 bit checksum is converted to two ASCII characters by taking the upper and lower
nibbles, adding 30h to each, and placing the most significant character first in the data message.
B.2.1.4.1 Airport Ident Output
This message is used to output the selected airport ident.
Message Format
$PMRRC04tiiii<chksum><cr>
04 ..............message id
t .................list type, outputs a 1
iiii ..............ident, four character ASCII
Example Message
$PMRRC041SLE<space>99<cr>
Output ident of “SLE” for the following frequency information.
B.2.1.4.2 Frequency Data Output
This message is used to output the airport frequency information for the previously output ident.
Message Format
$PMRRC05tfmk<chksum><cr>
05 message
id
t list type, input 1
f frequency type:
0 = TWR, tower frequency 8 = CTF, common traffic advisory frequency
1 = GND, ground frequency 9 = DEP, departure
2 = ATS, for ATIS : (3Ah) = FSS, flight service station
3 = ATF, air traffic frequency ; (3Bh) = RFS, for remote flight service station
4 = APP, for approach < (3Ch) = UNI, for unicom
5 = ARR, for arrival = (3Dh) = MF, mandatory frequency
6 = AWS, automatic weather station > (3Eh) = CTR (Center)
7 = CLR, clearance/delivery ? (3Fh) = undefined, for other frequency types
mk frequency:
m = desired frequency in MHz in hexadecimal, where m = desired frequency - 30h , with the
desired frequency in the range of 118 to 136 MHz, or 162 MHz.
k = desired frequency in kHz where k = (desired frequency / 25 kHz) + 30h, with the desired
frequency in the range of 000 to 975 kHz in 25 kHz steps, or 0 to 39.