442703/B
231
Note
TherearenocommonstandardforRS-422pinconguration.Anymanufacturermay
choosetheirownconnectorpinsforthevarioussignalsused.Inordertomakethe
RS-422connectiontoyourperipheraldeviceworkproperly,youmustalwaysconsultthe
relevantinstructionsprovidedbythedevicemanufacturer.
Useacablewithtwistedpairs.
FormoreinformationabouttheRS-422serialcommunicationstandard,see(for
example):
•https://en.wikipedia.org/wiki/RS-422
RS-485serialcommunication
RS-485(alsoknownasTIA-485–A)isastandarddeningtheelectricalcharacteristics
ofdriversandreceiversforuseinbalanceddigitalmultipointsystems.Thestandard
ispublishedbytheTelecommunicationsIndustryAssociation/ElectronicIndustries
Alliance(TIA/EIA).DigitalcommunicationsnetworksimplementingtheRS-485
standardcanbeusedeffectivelyoverlongdistancesandinelectricallynoisy
environments.Multiplereceiversmaybeconnectedtosuchanetworkinalinear,
multi-dropconguration.
RS-485offersdatatransmissionspeedsof35Mbit/supto10mand100kbit/sat1200
m.Sinceitusesadifferentialbalancedlineovertwistedpair(likeRS-422),itcanspan
relativelylargedistances(typicallyupmaximum1200m).IncontrasttoRS-422,which
hasasingledrivercircuitwhichcannotbeswitchedoff,RS-485driversneedtobeput
intransmitmodeexplicitlybyassertingasignaltothedriver.ThisallowsRS-485to
implementlinearbustopologiesusingonlytwowires.Theequipmentlocatedalonga
setofRS-485wiresareinterchangeablycallednodes,stationsordevices.
RS-485,likeRS-422,canbemadefull-duplexbyusingfourwires.SinceRS-485isa
multi-pointspecication,however,thisisnotnecessaryinmanycases.
Note
TherearenocommonstandardforRS-485pinconguration.Anymanufacturermay
choosetheirownconnectorpinsforthevarioussignalsused.Inordertomakethe
RS-485connectiontoyourperipheraldeviceworkproperly,youmustalwaysconsultthe
relevantinstructionsprovidedbythedevicemanufacturer.
Useacablewithtwistedpairs.
FormoreinformationabouttheRS-485serialcommunicationstandard,see(for
example):
•https://en.wikipedia.org/wiki/RS-485
Cablelayoutandinterconnections
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