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Transfer Mode Field
I/O Format Field
Interface Setup Submenu
Page
REFERENCE
Main Menu—
Interface Setup
Submenu
Interface Setup
The GPS 12CX’s interface page lets you specify the
formats for connecting external devices. There are six
options: GRMN/GRMN, None/None, RTCM/None,
RTCM/NMEA, NMEA/NMEA, and None/NMEA. Each
option lists the input format first, followed by the output
format.
To select an I/O format:
1. Highlight the I/O field and press
ENTER
.
2. Select the desired setting and press
ENTER
.
The GRMN/GRMN setting is a proprietary format
that lets you exchange information such as waypoints,
routes, and track logs between two GARMIN GPS units
or the GPS 12CX and a PC. The transfer mode field is
directly below ‘GRMN/GRMN’, and allows you to specify
what information to request or send to a second GPS
unit. The ‘Host’ setting lets you control all data transfer
functions from the second GPS unit or a PC.
To select a transfer mode:
1. Highlight the transfer mode field and press
ENTER
.
2. Select a desired setting, and press
ENTER
.
To disable all interfacing capabilities, select the ‘None/
None’ setting. If you want to output NMEA data without
any differential input capability, select ‘None/NMEA’.
Interface Setup: DGPS
The last two format settings allow the differential-
ready GPS 12CX to accept RTCM DGPS corrections in
RTCM 104 version 2.0 format. Using DGPS corrections
will improve receiver accuracy to 1-5 meters, regardless
of errors induced by the U.S. Dept. of Defense Selective
Availability (SA) program. Two RTCM options are avail-
able: ‘RTCM/NONE’, which allows connection to a bea-
con receiver with no output capability; and ‘RTCM/
NMEA’, which allows DGPS input and NMEA output.
When ‘RTCM/NMEA’ is selected, the GPS 12CX will
either automatically try to tune the last frequency and bit
rate you selected or will switch to the default frequency of
304.0 kHz with a bit rate of 100 bps if no previous beacon
has been tuned. (You may also enter your own frequency
and bit rate if desired.) This information is used to tune/
control an optional GARMIN GBR 21 differential beacon
receiver.
Note: Use the ‘RTCM/NONE’ setting if your beacon
receiver does not support these software-driven controls.