Tait T2000-A76 Operation Manual - page 10
10
M2303-00-P00-805
March 2003
RS232 from Remote Radio to GPS Receiver
The NMEA data transfer between the Remote AVL radio and the GPS receiver uses only the RXD data line. CTS
and RTS are used to active/deactivate the Aux Control line and Emergency mode respectively.
NMEA-0183 RMC Sentence Format
The NMEA RMC sentence is sent by the GPS receiver to the A76 in the remote AVL radio.
NMEA-0183 is a serial communication standard for encoding and sending GPS and other navigational data
between devices. All characters are ASCII (plus carriage return and line feed).
The data is transmitted as sentences, beginning with a $, a two letter sender ID, a three letter sentence ID,
followed by data fields separated by commas. The sentence is terminated with a checksum and a carriage
return and line feed. A sentence can contain up to 82 characters.
If a data field is empty, a comma is still inserted.
This application of the NMEA standard uses the RMC sentence format which is especially formulated for AVL
data.
The RMC sentance structure structure is:
$ - - RMC,hhmmss.ss, A,4925.345,N,yyyyy.yy,a,x.x, x.x,ddmmyy,x.x,a*hh
sentence part
information type
Definition
- -
GPS receiver ID
hmmss.ss
time (UTC)
hh = hours : two fixed digits
mm = minutes : two fixed digits
ss.ss = seconds : two fixed digits plus two optional deci-
mal points
A
status
A navigation receiver warning.
A = valid data
V = invalid data
4925.345
latitude
49 degrees : two fixed digits
25.345 minutes : two fixed digits plus up to three
optional decimal points