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Section-4 Theory

October 17, 2013

4‐2

WARNING:Disconnectprimarypower priortoservicing. 888‐2693‐004

4.2.1 LPULCDandFrontControlPanel

Thefrontcontrolpanelofthe lowpowerunit(LPU)servesastheprimarycontrolinterfaceforstandaloneUAXseries

transmitters.Additionally,dualdrivetransmittersmaycontainatransmittercontrolunit(TCU)servingasagateway

tothetwoLPUs.ThefunctioningoftheTCUisaddressedlaterinthissection.

TheLPUfr

ontpanelisanFPGA‐baseddesignthatservesasauserinterfaceandacommonbridgetotheexciterand

poweramplifiersections.Thisrelationshipis illustratedinFigure4‐1.Thefr

ontpanelhasthenecessarybuttonsfor

transmitterope

rationsuchason,off,powerraise/lower,remoteenable/disable,aswellasselectionandnavigation

keysfortheLCDdisplay.ThefrontpanelalsohasaseriesofstatusLEDs:TSInput,DriveChain,PowerAmp,Power

Supply,Output,System,andMute.

Thefr

ontpanelFPGAcommunicateswiththecontrolCPUonsignalprocessorboardviaadedicatedSPI(Serial

PeripheralInterface)bus.TheSPIbusisusedtoconfiguretheFPGA onboot‐upaswellascontroltheLCD,assert/

removecommands,gathertransmitterdata,andrespondtobuttonpressesinnormaloper

ation.

Th

efrontpanelFPGAalsointerfacestotheamplifiersthroughtheampcontrolboard.Thefrontpanelandamp

controlsharethreeparallel lines(Master/Slave,Interlock,andRFMute)aswellasadedicatedRS‐485bus.Whenan

on/offorre‐strikecommandisissuedtothefrontpanelFPGA,theFPGAmi

micsthecommandovertheRS‐485bus

totheampcontrolboard.TheMaster/Slaveparallellinetellstheampcontrolboardthatitisthemasterofthe

externalRS485bus.Thesignificanceofmastervs.slavestatusisdiscussedfurtherinSection4.2

.2.TheRFMuteand

Interlocklin

esallowcontactclosuresfromoutsidetheLPUtomomentarilymuteitsRFoutput(Mute)orforcea

transmitteroffcommand(Interlock).

4.2.2 TransmitterRS‐485Bus

ThededicatedRS485serialconnectionbetweenthefrontpanelandampcontrollerisusedtogathertransmitter

data.Thefrontpanelisalwaysthe“master”oftheRS‐485businternaltotheLPU.

WhenaTC

Uisinstalledinadualdrivesystem,theLPUsautomaticallyrecognizeitspresenceandrunineither

masterorslavemodewithregardstotheexternalRS‐485serialbusthroughtherestofthetransmittersystem.

WhenanLPUisinmastermode,theRS‐485connectiontotheex

ternaltransmittercomponentsremainsintact,

allowingthefrontpanelRS‐485“master”tocommunicatewiththeentiretransmitter.Thisrelationshipisillustrated

inFigure4‐2.

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