User guide

Rev 3.0D Jul.09 88
10
10: Configuring Modbus/BSAP
• Configuring the Raven
XT at the Polling
Host for Modbus on
UDP
• Configuring the
Remote Raven XTs
for Modbus with UDP
TheRavenXTsupportsModbusASCII,ModbusRTU,BSAP,
andcanalsoemulateotherprotocolslikeDF1orothersusing
itsModbusVariablefeature.
Modbus Overview
TheModbusProtocol,developedbyModiconin1979,
providesforclient‐server(alsoreferredtoasmaster‐slave)
communicationsbetweenintelligentdevices.Asadefacto
standard,itisthemostwidelyusednetworkprotocolinthe
industrialmanufacturingenvironmenttotransferdiscrete/
analogI/Oandregisterdatabetweencontroldevices.
Modbus,
BSAP,andotherModbusvariationsareoftenusedin
conjunctionwithtelemetrydevices.
Tip: This section is just a brief overview of Modbus. For more infor-
mation, refer to your Modbus equipment distributor or manufacturer or
http://www.modbus.org.
Te l e m e t r y
Telemetryisanautomatedcommunicationsprocessbywhich
dataiscollectedfrominstrumentslocatedatremoteorinacces
‐
siblepointsandtransmittedtoreceivingequipmentfor
measurement,monitoring,display,andrecording.Trans
‐
missionoftheinformationmaybeoverphysicalpairsofwires,
telecommunicationcircuits,radiosorsatellite.
Remote Terminal Unit (RTU)
Modbuswasoriginallydesignedtobeusedinaradio
environmentwherepacketsarebroadcastfromacentral
station(alsocalledmasterorhost)toagroupofremoteunits.
Eachremoteunit,RemoteTerminalUnit(RTU),hasa
hexidecimalidentificationnumber(ID).Thefirstpartof the
broadcastpacketcontains
anRTUIDwhichcorrespondstothe
IDofoneoftheremoteunits.TheModbushostlooksforthe
IDandsendstoonlytheunitwiththematchingID.TheRTU
wouldthenreplybacktothecentralstation.