Raymarine RAY70 - System Protocols

3.8Systemprotocols
Yourproductcansendandreceiveposition
information,e.g.latitudeandlongitudeusinganyof
thefollowingprotocols:
•SeaTalk
ng
•NMEA2000
•NMEA0183
Usingtheseprotocolsenablesyourradiotosend
positioninformationtootherdevicesinyoursystem
wheneveritreceives:
•aresponsetoaDSCpositionrequest.
•aDSCdistresscall
Note:Youmayndthatyourproductorsystem
doesnotusealloftheprotocolsdescribedinthis
section.
Seatalk
ng
SeaTalk
ng
(NextGeneration)isanenhancedprotocol
forconnectionofcompatiblemarineinstruments
andequipment.ItreplacestheolderSeaTalkand
SeaTalk
2
protocols.
SeaTalk
ng
utilizesasinglebackbonetowhich
compatibleinstrumentsconnectusingaspur.Data
andpowerarecarriedwithinthebackbone.Devices
thathavealowdrawcanbepoweredfromthe
network,althoughhighcurrentequipmentwillneed
tohaveaseparatepowerconnection.
SeaTalk
ng
isaproprietaryextensiontoNMEA2000
andtheprovenCANbustechnology.Compatible
NMEA2000andSeaT alk/SeaT alk
2
devicescan
alsobeconnectedusingtheappropriateinterfaces
oradaptorcablesasrequired.
NMEA2000
NMEA2000offerssignicantimprovementsover
NMEA0183,mostnotablyinspeedandconnectivity.
Upto50unitscansimultaneouslytransmitand
receiveonasinglephysicalbusatanyonetime,
witheachnodebeingphysicallyaddressable.The
standardwasspecicallyintendedtoallowfor
awholenetworkofmarineelectronicsfromany
manufacturertocommunicateonacommonbusvia
standardizedmessagetypesandformats.
NMEA0183
TheNMEA0183DataInterfaceStandardwas
developedbytheNationalMarineElectronics
AssociationofAmerica.Itisaninternational
standardtoenableequipmentfrommanydifferent
manufacturerstobeconnectedtogetherandshare
information.
TheNMEA0183standardcarriessimilarinformation
toSeaTalk.Howeverithastheimportantdifference
thatonecablewillonlycarryinformationinone
direction.ForthisreasonNMEA0183isgenerally
usedtoconnectadatareceiverandatransmitter
together,e.g.acompasssensortransmitting
headingtoaradardisplay.Thisinformationis
passedin‘sentences’,eachofwhichhasathree
lettersentenceidentier.Itisthereforeimportant
whencheckingcompatibilitybetweenitemsthatthe
samesentenceidentiersareusedsomeexamples
ofwhichare:
•VTG-carriesCourseandSpeedOverGround
data.
•GLL-carrieslatitudeandlongitude.
•DBT-carrieswaterdepth.
•MWV-carriesrelativewindangleandwindspeed
data.
NMEABaudrates
TheNMEA0183standardoperatesatanumber
ofdifferentspeeds,dependingupontheparticular
requirementorequipmentcapabilities.Typical
examplesare:
•4800baudrate.Usedforgeneralpurpose
communications,includingFastHeadingdata.
•38400baudrate.UsedforAISandotherhigh
speedapplications.
Planningtheinstallation
21