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Sierra Wireless 20070914 Modem User Manual

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Raven iDEN

69 20070914

TheRTUconnectstophysicalequipmentsuchasswitches,

pumps,andotherdevicesandmonitorsandcontrolsthese

devices.TheRTUcanbepartofanetworksetupforSuper

‐

visoryControlandDataAcquisition.

Supervisory Control and Data Acquisition (SCADA)

SupervisoryControlandDataAcquisition(SCADA)describes

solutionsacrossalargevarietyofindustriesandisusedin

industrialandengineeringapplicationstomonitorandcontrol

distributedsystemsfromamasterlocation.SCADAencom

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passesmultipleRTUs,acentralcontrolroomwithahost

computer(ornetwork),andsomesortofcommunicationinfra

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structure.

SCADAallowsfor“supervisory”controlofremotedevicesas

wellasacquiringdatafromtheremotelocations.Program

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mableLogicControllersallowforahigherdegreeof

automatedSCADA.

Programmable Logic Controller (PLC)

AProgrammableLogicController(PLC)isasmallindustrial

computerwhichgenerallymonitorsseveralconnectedsensor

inputsandcontrolsattacheddevices(motorstarters,solenoids,

pilotlights/displays,speeddrives,valves,etc.)accordingtoa

user‐createdprogramstoredinitsmemory.Containinginputs

andoutputssimilartoanRTU,PLCsarefrequently

usedfor

typicalrelaycontrol,sophisticatedmotioncontrol,process

control,DistributedControlSystemandcomplexnetworking.

Modbus TCP/IP

ModbusTCP/IPsimplytakestheModbusinstructionsetand

wrapsTCP/IParoundit.SinceTCP/IPisthecommunications

standardfortheInternetandmostnetworkedcomputers,this

providesasimplerinstallation.ModbusTCP/IPusesstandard

Ethernetequipment.

Raven Modbus on UDP

WhenSierraWirelessAirLinkmodemsareusedinplaceof

radios,aRavenisconnectedtothecentralstation(host)and

aRavenisconnectedtoeachremoteunit.WhentheRavenis

configuredforModbuswithUDP,theRavenconnectedtothe

hostcanstorealistofIPaddressesor

nameswithmatching

IDs.Whenthehostatthecentralstationsendsserialdataasa

pollrequest,theRavenatthehostmatchestheRTUIDtoa

correspondingIPofaRavenataremoteunit.AUDPpacketis

assembledencapsulatingtheRTUIDandserialdata

trans‐

mittedfromthehost.TheUDPpacketisthentransmittedto

thespecificRavenattheremoteunitmatchingtheRTUID.

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