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4ExpansionOptions
4.1CustomFPGACode
4.2ExpansionSlot
4.3OptionalUSBSPIInterface
ExpansionOptions
TheEVMoffersseveralexcitingpossibilitiestoexpandthecapabilitiesoftheEVM.Thisallowstheutmost
flexibilitywhenprototypinganADCcircuitunderconditionsthatmimictheendsystem,withouttheneedto
developacustomprototypeboard.
UsingastandardJTAGinterfaceonJP1,usershavetheabilitytoloadcustomlogicontotheFPGA,
rapidlyspeedingupdigitaldevelopmenttime.Thisallowstheflexibilityofprototypinganddebuggingan
ADCdigitalinterfacedesignbeforedevelopingapplication-specifichardware.
TotakeadvantageoftheonboardFPGA,userscandownloadthefreeXilinxWebPACK™fromtheXilinx
Website.SelecttheXC3S250E-4FT256astheFPGAandtheXCF16PFSG48asthePROM.
Note:SeetheXilinxSpartan-3EWebsiteforcompletedocumentationoftheFPGAat:
http://direct.xilinx.com/bvdocs/publications/ds312.pdf
Schematically,theFPGAisconfiguredinBPImode,anditsamplesFPGApinsM2,M1,andM0whenthe
FPGA'sINIT_Bisbroughtlow.DependingofthestatusofM0,itbootsfromeitherthetoporthebottomof
thePROMcontents.ThePROMallowsforthestorageoftwoFPGAbitfiles.Initsdefaultcondition,the
EVMstoresonefileforADCCMOSoutputatthebeginningofthePROMaddressspaceandonefilefor
ADCLVDSoutputattheendofthePROMaddressspace.
Note:WhencreatingcustomFPGAcode,storeanycustom-developedbitfilesforADCCMOS
operationinthePROMrevision0space,andstoreanycustom-developedFPGAcodefor
ADCLVDSoperationinthePROMrevision1space.
ForthoseuserswhomakeuseofacustomFPGAprogramontheEVM,J5andJ6providean
expansion-slotcapability.Userscandesigndaughtercardsorbreakoutboardstomakeuseoftheunused
FPGAI/Opinswhicharebroughtouttotheheaders.
Note:TheEVMprovides5VfromJ14topin1ofbothJ5andJ6.Thiscanbeusedtoprovide
powertoanydesigneddaughtercards.
Inmostcases,userscanusetheADCparallelinterfacemodetochangetheoperationalmodesofthe
ADC.ForusersrequiringSPIcontroloftheADC,TIhasdevelopedanoptionalUSBdaughtercardthat
plugsintotheexpansionslot.WiththeUSBdaughtercard,userscanuseaPCinterfacetocommunicate
totheADCthree-wireSPIinterface,whichallowsforcompletecontroloftheADCregistermap.Contact
thefactoryforthisoptionalaccessory.
SLWU028B–January2006–RevisedNovember200613
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