简单化的AD转换器软件接口

Integratinganalog-to-digitalconverters(ADCs)featuringbinary-

codeddecimal(BCD)outputsfordisplayinterfaceofferanumber

ofexcellentfeatures,aswellashighresolution,ataverylowcost.

Theseadvantagesincludeauto-zeroing,sign-magnitudecoding,

noiseaveraging,andhighimpedanceinputsandarealsoattrac-

tiveformicroprocessor-basedsystems.Unfortunately,many

display-orientedADCsaredifficulttointerfaceduetothemulti-

plexedBCDformatoftheoutputs.Anexceptionisthe4-1/2digit

TC7135ADC,whichprovidesa"strobe"output.AN785SimplifyA/DConverterInterfacewithSoftwareAuthors:GaryGrandboisandWesFreeman,INTERFACEHARDWAREMicrochipTechnology,Inc.ThecompleteTC7135-to-18255AhardwareinterfaceisshowninFigure1.TheonlydigitstrobeusedisDS5(MSD),andtheBUSYoutputisignored.TounderstandwhytheotherdigitstrobesarenotINTRODUCTION