Raymarine c95 - System Protocols

3.8Systemprotocols
YourMultifunctionDisplaycanconnecttovariousinstrumentsand
displaystoshareinformationandsoimprovethefunctionalityof
thesystem.Theseconnectionsmaybemadeusinganumberof
differentprotocols.Fastandaccuratedatacollectionandtransferis
achievedbyusingacombinationofthefollowingdataprotocols:
•SeaT alk
hs
•SeaT alk
ng
•NMEA2000
•SeaT alk
•NMEA0183
Note:Youmayndthatyoursystemdoesnotuseallofthe
connectiontypesorinstrumentationdescribedinthissection.
SeaTalk
hs
SeaTalk
hs
isanethernetbasedmarinenetwork.Thishighspeed
protocolallowscompatibleequipmenttocommunicaterapidlyand
sharelargeamountsofdata.
InformationsharedusingtheSeaTalk
hs
networkincludes:
•Sharedcartography(betweencompatibledisplays).
•Digitalradardata.
•Sonardata.
Seatalk
ng
SeaTalk
ng
(NextGeneration)isanenhancedprotocolforconnection
ofcompatiblemarineinstrumentsandequipment.Itreplacesthe
olderSeaTalkandSeaTalk
2
protocols.
SeaTalk
ng
utilizesasinglebackbonetowhichcompatible
instrumentsconnectusingaspur.Dataandpowerarecarriedwithin
thebackbone.Devicesthathavealowdrawcanbepoweredfrom
thenetwork,althoughhighcurrentequipmentwillneedtohavea
separatepowerconnection.
SeaTalk
ng
isaproprietaryextensiontoNMEA2000andtheproven
CANbustechnology.CompatibleNMEA2000andSeaT alk/
SeaTalk
2
devicescanalsobeconnectedusingtheappropriate
interfacesoradaptorcablesasrequired.
NMEA2000
NMEA2000offerssignicantimprovementsoverNMEA0183,most
notablyinspeedandconnectivity.Upto50unitscansimultaneously
transmitandreceiveonasinglephysicalbusatanyonetime,
witheachnodebeingphysicallyaddressable.Thestandard
wasspecicallyintendedtoallowforawholenetworkofmarine
electronicsfromanymanufacturertocommunicateonacommon
busviastandardizedmessagetypesandformats.
SeaTalk
SeaTalkisaprotocolwhichenablescompatibleinstrumentsto
connecttoeachotherandsharedata.
TheSeaTalkcablesystemisusedtoconnectcompatible
instrumentsandequipment.Thecablecarriespoweranddataand
enablesconnectionwithouttheneedforacentralprocessor.
AdditionalinstrumentsandfunctionscanbeaddedtoaSeaTalk
system,simplybypluggingthemintothenetwork.SeaT alk
equipmentcanalsocommunicatewithothernon-SeaTalkequipment
viatheNMEA0183standard,providedasuitableinterfaceisused.
NMEA0183
TheNMEA0183DataInterfaceStandardwasdevelopedby
theNationalMarineElectronicsAssociationofAmerica.Itisan
internationalstandardtoenableequipmentfrommanydifferent
manufacturerstobeconnectedtogetherandshareinformation.
TheNMEA0183standardcarriessimilarinformationtoSeaTalk.
Howeverithastheimportantdifferencethatonecablewillonly
carryinformationinonedirection.ForthisreasonNMEA0183is
generallyusedtoconnectadatareceiverandatransmittertogether,
e.g.acompasssensortransmittingheadingtoaradardisplay.This
informationispassedin‘sentences’,eachofwhichhasathree
lettersentenceidentier.Itisthereforeimportantwhenchecking
compatibilitybetweenitemsthatthesamesentenceidentiersare
usedsomeexamplesofwhichare:
•VTG-carriesCourseandSpeedOverGrounddata.
•GLL-carrieslatitudeandlongitude.
•DBT-carrieswaterdepth.
•MWV-carriesrelativewindangleandwindspeeddata.
NMEAbaudrates
TheNMEA0183standardoperatesatanumberofdifferent
speeds,dependingupontheparticularrequirementorequipment
capabilities.Typicalexamplesare:
•4800baudrate.Usedforgeneralpurposecommunications,
includingFastHeadingdata.
•9600baudrate.UsedforNavtex.
•38400baudrate.UsedforAISandotherhighspeedapplications.
Planningtheinstallation
27