ComNav 2001 - Page 30

ComNav 2001 Autopilot System
P/N 29010017 V1.0 - 30-
The NMEA 0183 data format is becoming the
standard for communication between marine
electronic devices. A factory modification is
required to obtain this output.
The data sentences transmitted are HDM (present
Magnetic Heading) and HCC (Uncorrected
Compass Heading). The HDT (present True
Heading) is also transmitted if the autopilot is
using a gyrocompass.
The NMEA 0183 format is a two wire signal.
One wire connects to TX CLOCK, terminal 22 in
the autopilot distribution box. The other wire
connects to COMMON, terminal 25 in the
autopilot distribution box. The wire should be
shielded, with the shield also connected to the
COMMON terminal, and unterminated at the
other end, to prevent the emission of any radio
noise.
The signal is 5 volts in amplitude, and transmitted
at 4800 baud. The output has enough drive to
transmit to 2 standard NMEA 0183 'listeners', ie.
both a Satnav and Satcom. The information is
transmitted twice a second. Dip Switches 3 and 4
must be in the "closed" or "on" position.