NM-541 is a four or five input channel multiplexer with five output channels NMEA-0183 data multiplier. It enables combining and multiplying of all NM-0183 sources to the navigational instruments through five talker ports and PC connection through RS-232, USB and an optional Ethernet interface.
NM-541 acquires the NM-0183 signals from the four optically isolated inputs and the RS-422 (Ine) or USB or the RS232 or Ethernet input port, combines the data and outputs them to the five general output ports (RS485 and Out1-Out4), the RS-232 the USB and the Ethernet (optional) output ports.
1. Configurable input reception speed for Input ports: The speed for the received data in the input ports Ind and Ine can be configured via the dip switch array according to table 1. The speed for the input ports Ina to Inc is fixed to 4.800 bps.
2. Configurable output transmission speed: The output speed for the combined data stream of the five input ports (Ina-Ind and Ine or RS232 or USB or Ethernet) is user selectable via dip-switches and can be set to 4.800, 9.600, 19.200, 38.400, 57.600 and 115.200 baud.
3. Input Autosense: The NM-541 senses a correct NMEA signal application to any of the four inputs (Ina-Ind) and flashes the RXD LED. If no or incorrect signal is applied to all four inputs the RXD LED remains in the OFF condition. The existence of an input signal in the port Ine or RS232 or USB or Ethernet is indicated from the INE LED status. The flashing of INE LED although does not indicate a correctly applied signal.
4. Data overflow indication: The NM-541 has an overflow indication via the OVF LED. When an overflow occurs some of the last inputted data will not be transmitted. This is normal when connecting to instruments transmitting great amounts of data, and can be fully resolved if the output transmission speed is configured to a higher value.
5. Watchdog: The integrated watchdog reset feature will bring NM-541 back from any unresponsive state into normal operation.
The NM541 has five input ports. The Input ports Ina-Ind are optically isolated and can be connected to any instrument intended for marine use that can output NMEA-0183 signals following the 4.800/8/N/1 serial protocol and carried in a TTL, RS232 or RS485/RS422 electrical levels.
The fifth input port can be one of the Ine (RS422 input) or the RXD channel of the RS232, USB or Ethernet (optional) port. The routing of the input data in any of these ports is achieved automatically. Only one of the Ine, RS232, USB and Ethernet receiving channel should be connected as the fifth input port of the NM541 else the data will be corrupted and filtered out of the combined stream. The baud rate of the signals in the fifth port follows the selection of the speed of the output ports. This feature allows connection of the NM-541 to Automatic Identification Systems (AIS) at 38.400 baud or to another NM541 in cascaded topology.
Each of the five general purpose talker ports transmit NMEA sentences in both RS422 and TTL signal levels, depending on the connection topology chosen (see figure 1, 2 and 3), and can fan out one instrument. Current drawn from each port is efficient enough to drive any NMEA compatible instrument.
The RS-232, USB and Ethernet ports can deliver NMEA sentences to any modern computer running the appropriate software on Windows 2000 or later provided that serial communication follows the 4.800, 9.600, 19.200, 38.400, 57600 or 115.200/8/N/1 standard. These ports are not optically isolated and should be used when proper isolation is achieved or if the computer is supplied from an isolated power supply in order to avoid current leakage
Technical Details and specification