NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
Page 4 of 6
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Great Lakes Marine Specialties
Great Lakes Marine Specialties
Great Lakes Marine Specialties
Great Lakes Marine Specialties
800
800
800
800----821
821
821
821----0207 USA & Canada
0207 USA & Canada
0207 USA & Canada
0207 USA & Canada
952
952
952
952----925
925
925
925----1285 All other Countries
1285 All other Countries
1285 All other Countries
1285 All other Countries
Operation
The listener (IN1A,IN1B,....IN4A,IN4B) ports
The N183-41 features four independent NMEA-0183 listener ports. Each port receives data
from the instrument connected to it on a character-by-character basis and is stored in memory
exclusive to that port. Upon reception of a complete message, (i.e., a string of ASCII characters
terminated by a [CR][LF]), the message is transferred to the RS-232 output. Messages from each
input port are transferred to the output in the order that they are completed.
The talker (TLKA,TLKB) port
The N183-41 features one NMEA-0183 talker port. The N183-41 receives data to be sent out of
the talker port from the host computer via the RS-232 port on a character-by-character basis
storing the data in the talker buffer until a complete message is received. (A complete NMEA
0183 message is defined as a string of ASCII characters beginning with a $, and terminated by a
[CR][LF]. (See the Appendix A for details.) As soon as a complete message is received from the
computer, it is transmitted out the talker port.
The RS-232 (RX,COM,TX) port
A standard RS-232 port is provided for the communication interface to the host computer. This
port is intended for transmitting and receiving NMEA-0183 listener/talker messages to and from
the host computer. This port is also compatible with NMEA-0183 at its default setting of 4800
baud. Listed below are a series of control characters which are available to the host for control-
ling the N183-41:
^R
= Reset the N183-41
^S
= Stop sending data
^C
= Restart sending data
^H
= Change Baud rate from 4800-9600
^L
= Change Baud rate from 9600 to 4800
Note: On initial power-up, the N183-41 defaults to 4800 Baud and automatically sends data
once it is received without any user intervention.
Programming
This section describes the communication protocol and programming features of the N183-41.
Data Acquisition
Acquiring data from marine navigational instruments is the primary function of the N183-41.
Under the NMEA 0183 specification, all data is transmitted as fields of ASCII characters assem-
bled into specific messages. The format of every NMEA 0183 message is defined the standard.
There are three basic sentence structures defined by the standard;
