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3EVMOperation
3.1DefaultSettings
3.2HostProcessorInterface
3.3EVMStacking
EVMOperation
ThissectioncoverstheoperationoftheEVMindetail,inordertoprovideguidancetotheuserin
evaluatingtheonboardDACaswellashowtointerfacetheEVMtoaspecifichostprocessor.Refertothe
DAC8555datasheetforinformationaboutitsserialinterfaceandotherrelatedtopics.TheEVMboardis
factory-testedandconfigured.
TheEVMissettoitsfactorydefaultconfigurationasdescribedinTable2tooperatein5Vmode.
Table2.FactoryDefaultJumperSettings
ReferenceJumperPositionFunction
JMP1CLOSEENABLEpinistiedtoDGND
JMP2CLOSELDACpinistiedtoDGND.SoftwareLDACisused.
JMP3CLOSERSTSELpinistiedtoDGND.
JMP4OPENRSTpinistiedtoV
DD
.
V
REF
Hisnotroutedtotheinvertinginputoftheopampforvoltageoffsetwithgainof2
JMP5OPEN
output.
JMP6OPENOutputopampU2isnotconfiguredforagainof2.
JMP71-2AnalogsupplyfortheDAC8555is+5V
A
.
JPM81-2OnboardexternalbufferedreferenceU3isroutedtoV
REF
H.
JMP91-2V
REF
ListiedtoAGND.
JMP101-2NegativesupplyrailofU2opampissuppliedwithV
SS
.
JMP111-2DACoutputA(V
OUT
A)isroutedtoJ4-2.
JMP121-2DACoutputB(V
OUT
B)isroutedtoJ4-4.
JMP131-2DACoutputC(V
OUT
C)isroutedtoJ4-6.
JMP141-2DACoutputD(V
OUT
D)isroutedtoJ4-8.
JMP151-2J4-1isconnectedtothenoninvertinginputoftheoutputopampU2.
JMP161-2J4-5isconnectedtotheoutputoftheopampU2.
ThehostprocessordrivestheDAC.Thus,properDACoperationdependsonasuccessfulconfiguration
betweenthehostprocessorandtheEVMboard.Inaddition,properlywrittencodeisalsorequiredto
operatetheDAC.
Asdiscussedearlier,acustomcablecanbemadespecifictothehostinterfaceplatform.TheEVMallows
interfacetothehostprocessorthroughheaderconnectorJ2fortheserialcontrolsignalsandtheserial
datainput.TheoutputcanbemonitoredthroughheaderconnectorJ4.
AninterfaceadaptercardisalsoavailableforspecificTIDSPDSKsaswellasanMSP430-based
microprocessor(seeSection1.3ofthismanual).Usingtheinterfacecardalleviatesthetedioustaskof
buildingcustomizedcablesandallowseasyconfigurationofasimpleevaluationsystem.
TheDAC8555interfaceswithanyhostprocessorcapableofhandlingSPIprotocolsorthepopularTI
DSPs.FormoreinformationregardingtheDAC8555datainterface,pleaserefertotheDAC8555
datasheet.
StackingmultipleEVMSispossibleifthereisaneedtoevaluatetwoDAC8555s,yieldingatotalofeight
outputchannels.AmaximumoftwoEVMscanbestackedsincetheoutputterminal,J4,dictatesthe
numberofDACchannelsthatcanbeconnectedwithoutcolliding.Table3showshowtheDACoutput
channelsaremappedintotheoutputterminal,J4,withrespecttothejumperpositionsofJMP11,JMP12,
JMP13,andJMP14.
DAC8555EVMUser'sGuide 16SLAU204–December2006
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