Nmea Interface To Other Equipment; Version - NorthStar MX500 Operator's & Installation Manual

Installation Manual

NMEA Interface to other Equipment

The MX500 meets NMEA 0183 version 2.3 electrically, and in protocol.
As version 2.1 is not necessarily compatible with the older version 1.5,
the differences in hardware are mentioned here to avoid possible con-
flicts:
Listener:
The listener input works with a threshold of 2 volts compared to the
former 4 volt. It is still an insulated input and, in general, there should not
be any interface problems receiving data from the older
standard.
Talker:
The talker output is a RS-422 output:
NMEA talker output B is active compared to GND or shield of the naviga-
tor. In the old version, output B was normally tied to GND or shield.
The maximum drive voltage between the talker A and B outputs is ±6
volt.
Compared to the former 0 to 15 volt output, the negative voltage
between the talker A and B output may be a problem on older
listeners which do not meet the new standard.
The minimum output voltage may be as low as ±2 volt. This is not
compatible with the former 4 volt input threshold and may be the cause
of interface problems. If this is the case, try using an RS-232 to RS-422
convertor to interface with the MX 500 (see page 227). This may more
likely solve the problem. Otherwise third party conversion boxes may be
necessary.
Cables provided for the NMEA signals are shielded pairs. If extension
cables are needed, be sure to use similar shielded pair cables in order
to avoid spurious signal radiation. More than one NMEA listener can be
connected in parallel to the same NMEA talker. The maximum number
of listeners connected to a single talker is dependent on the combined
listener input impedance's, and the capacity available for data through-
put.
216
Installation Notes

Version 3.0