Specifications

Section-4 Theory
October 17, 2013
4‐2
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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.