Simrad ST90 - About Serial Lines

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Aboutseriallines
ApreferredmethodtoestablishcommunicationbetweentheST90andperipheral
devices,isbymeansofseriallines.Severalseriallinestandardsareavailable,each
withdifferentqualities.
Unlessotherwisespecied,thesecablesmustbeprovidedbytheinstallationshipyard.
RS-232serialcommunication
AnRS-232serialportwasonceastandardfeatureofapersonalcomputer,usedfor
connectionstomodems,printers,mice,datastorage,uninterruptiblepowersupplies,
andotherperipheraldevices.However,RS-232ishamperedbylowtransmission
speed,largevoltageswing,andlargestandardconnectors.[...]Nevertheless,
RS-232devicesarestillused,especiallyinindustrialmachines,networking
equipmentandscienticinstruments.
https://en.wikipedia.org/wiki/RS-232(September2015)
MaximumlengthforanRS-232serialcableistypically60meterswith2400bpsdata
rate,howeverthisdependsonthecablequality.Alwayscheckthecablemanufacturers
specicationsfortheactual"shuntcapacitance".Acommongureis47.5pF/m,which
givesamaximumcablelengthofabout50meters.
Note
MostRS-232cablesdonotsupportallthesignalsinthestandardRS-232specication.
Observethatlongrunsofunshieldedcablewillpickupnoiseeasily.Thisisbecause
theRS-232signalsarenotbalanced.
EventhoughastandardexistforRS-232pinconguration,certainmanufacturermay
stillchoosetheirownconnectorpinsforthevarioussignalsused.Inordertomakethe
RS-232connectiontoyourperipheraldeviceworkproperly,youmustalwaysconsultthe
relevantinstructionsprovidedbythedevicemanufacturer.
FormoreinformationabouttheRS-232serialcommunicationstandard,see(for
example):
•https://en.wikipedia.org/wiki/RS-232
RS-422serialcommunication
WhileRS-232isthemostcommonserialinterfaceforcommunicatingwithexternal
devicesusingtheNMEAstandard,itonlyallowsforonetransmitterandonereceiver
oneachline.
RS-422providesamechanismfortransmittingdataupto10Mbits/s.Thisinterface
formatusesabalancedsignalontwowires.Thisincreasesboththemaximumbaud
rateandthephysicallengthofthecable,anditreducesthenoise.Withahighquality
cable,youcanuseRS-422ondistancesupto1500meterseveninnoisyenvironments.
RS-422isalsospeciedformulti-dropapplications.Thismeansthatonetransmittercan
senddatatoupto10receivers.
SimradST90InstallationManual