3.7 System protocolsYour Multifunction Display can connect to variousinstruments and displays to share information andso improve the functionality of the system. Theseconnections may be made using a number ofdifferent protocols. Fast and accurate data collectionand transfer is achieved by using a combination ofthe following data protocols:• SeaTalkhs• SeaTalkng• NMEA 2000• SeaTalk• NMEA 0183Note: You may find that your system does notuse all of the connection types or instrumentationdescribed in this section.SeaTalkhsSeaTalkhs is an ethernet based marine network. Thishigh speed protocol allows compatible equipmentto communicate rapidly and share large amounts ofdata.Information shared using the SeaTalkhs networkincludes:• Shared cartography (between compatibledisplays).• Digital radar data.• Sonar data.SeatalkngSeaTalkng (Next Generation) is an enhanced protocolfor connection of compatible marine instrumentsand equipment. It replaces the older SeaTalk andSeaTalk2 protocols.SeaTalkng utilizes a single backbone to whichcompatible instruments connect using a spur. Dataand power are carried within the backbone. Devicesthat have a low draw can be powered from thenetwork, although high current equipment will needto have a separate power connection.SeaTalkng is a proprietary extension to NMEA 2000and the proven CAN bus technology. CompatibleNMEA 2000 and SeaTalk / SeaTalk2 devices canalso be connected using the appropriate interfacesor adaptor cables as required.NMEA 2000NMEA 2000 offers significant improvements overNMEA 0183, most notably in speed and connectivity.Up to 50 units can simultaneously transmit andreceive on a single physical bus at any one time,with each node being physically addressable. Thestandard was specifically intended to allow fora whole network of marine electronics from anymanufacturer to communicate on a common bus viastandardized message types and formats.SeaTalkSeaTalk is a protocol which enables compatibleinstruments to connect to each other and share data.The SeaTalk cable system is used to connectcompatible instruments and equipment. The cablecarries power and data and enables connectionwithout the need for a central processor.Additional instruments and functions can be added toa SeaTalk system, simply by plugging them into thenetwork. SeaTalk equipment can also communicatewith other non-SeaTalk equipment via the NMEA0183 standard, provided a suitable interface is used.NMEA 0183The NMEA 0183 Data Interface Standard wasdeveloped by the National Marine ElectronicsAssociation of America. It is an internationalstandard to enable equipment from many differentmanufacturers to be connected together and shareinformation.The NMEA 0183 standard carries similar informationto SeaTalk. However it has the important differencethat one cable will only carry information in onedirection. For this reason NMEA 0183 is generallyused to connect a data receiver and a transmittertogether, e.g. a compass sensor transmittingheading to a radar display. This information ispassed in ‘sentences’, each of which has a threeletter sentence identifier. It is therefore importantwhen checking compatibility between items that thesame sentence identifiers are used some examplesof which are:• VTG - carries Course and Speed Over Grounddata.• GLL - carries latitude and longitude.• DBT - carries water depth.• MWV - carries relative wind angle and wind speeddata.NMEA Baud ratesThe NMEA 0183 standard operates at a numberof different speeds, depending upon the particularrequirement or equipment capabilities. Typicalexamples are:• 4800 baud rate. Used for general purposecommunications, including FastHeading data.• 38400 baud rate. Used for AIS and other highspeed applications.38 gS Series
