2020 6 5 电子技术专业英语教程 1 Lesson19LogicGates 电子技术专业英语教程 冯新宇主编电子工业出版社 Unit7DigitalLogicCircuit 2020 6 5 电子技术专业英语教程 2 Lesson19LogicGates BackgroundsTexttourLanguageinuseVocabularyStructureReading writingtechniques 2020 6 5 电子技术专业英语教程 3 TerminologyORing或操作 或运算ANDing与操作 与运算Booleanalgebra 计 逻辑代数 布尔代数 Backgrounds 2020 6 5 电子技术专业英语教程 4 Texttour OutlineWhatis gates andBooleanalgebra NOTOperationTruthtableSymbolicofNOTgateExampleORoperationTruthtableSymbolicofORgateDiodeORgateExampleANDoperationTruthtableSymbolicofANDgateDiodeANDgateExample 2020 6 5 电子技术专业英语教程 5 Whatis gates andBooleanalgebra Digitalcircuitscontainhardwareelementscalled gates thatperformlogicoperationsonbinarynumbers Devicessuchastransistorscanbeusedtoperformthelogicoperations Booleanalgebraisamathematicalsystemthatprovidesthebasisfortheselogicoperations GeorgeBoole anEnglishmathematician introducedthistheoryofdigitallogic ThetermBooleanvariableisusedtomeanthetwo valuedbinarydigit1or0 Booleanalgebrausesthreebasiclogicoperationsnamely NOT OR andAND Theseoperationsaredescribednext 2020 6 5 电子技术专业英语教程 6 NOTOperation TheNOToperationinvertsorprovidestheonescomplementofabinarydigit Thisoperationtakesasingleinputandgeneratesoneoutput TheNOToperationofabinarydigitprovidesthefollowingresult NOT1 0NOT0 1 2020 6 5 电子技术专业英语教程 7 NOTOperation Truthtable Therefore NOTofaBooleanvariableA writtenas orA is1ifandonlyifAis0 Similarly is0ifandonlyifAis1 Thisdefinitionmayalsobespecifiedintheformofatruthtable Notethatatruthtablecontainstheinputsandoutputsofdigitallogiccircuits 2020 6 5 电子技术专业英语教程 8 NOTOperation SymbolicofNOTgate ANOTgateisalsoreferredtoasan inverter becauseitinvertsthevoltagelevels transistoractsasaninverter A0 voltattheinputgeneratesa5 voltoutput a5 voltinputprovidesa0 voltoutput Figure19 1NOTgate 2020 6 5 电子技术专业英语教程 9 NOTOperation Example The74HC04 or74LS04 isahexinverter14 pinchipcontainingsixindependentinvertersinthesamechipasshowninFigure19 2 ComputersnormallyincludeaNOTinstructiontoperformtheonescomplementofabinarynumberonabit by bitbasis An8 bitcomputercanperformNOToperationonan8 bitbinarynumber Forexample thecomputercanexecuteaNOTinstructiononan8 bitbinarynumber01101111toprovidetheresult10010000 Thecomputerutilizesaninternalelectroniccircuitconsistingofeightinverterstoinvertthe8 bitdatainparallel Figure19 2Pindiagramforthe74HC04or74LS04 HexInverter74LS04 2020 6 5 电子技术专业英语教程 10 ORoperation TheORoperationfortwovariablesAandBgeneratesaresultof1ifAorB orboth are1 However ifbothAandBarezero thentheresultis0 Aplussign logicalsum or symbolisnormallyusedtorepresentOR ThefourpossiblecombinationsofORingtwobinarydigitsare0 0 00 1 11 0 11 1 1 2020 6 5 电子技术专业英语教程 11 ORoperation TruthtableandSymbolicofNOTgate Atruthtableisusuallyusedwithlogicoperationstorepresentallpossiblecombinationsofinputsandthecorrespondingoutputs ThetruthtablefortheORoperationis Figure19 3ORgate 2020 6 5 电子技术专业英语教程 12 OROperation DiodeORgate Thediodeisaswitch anditcloseswhenthereisavoltagedropof0 6Vbetweentheanodeandthecathode Supposethatavoltagerangeof0to2Visconsideredaslogic0andavoltageof3to5Vislogic1 IfbothAandBareatlogic0 say1 5V withavoltagedropacrossthediodesof0 6Vtoclosethediodeswitches acurrentflowsfromtheinputsthroughRtoground andtheoutputCwillbeat1 5V 0 6V 0 9V logic0 Ontheotherhand ifoneorbothinputsareatlogic1 say4 5V theoutputCwillbeat4 5 0 6V 3 9V logic1 Therefore thecircuitactsasanORgate Figure19 4DiodeORgate 2020 6 5 电子技术专业英语教程 13 OROperation Example The74HC32 or74LS32 isacommerciallyavailablequad2 input14 pinORgatechip Thischipcontainsfour2 input l outputindependentORgatesasshowninFigure19 5 Figure19 5Pindiagramfor74HC32or74LS32 74LS32 2020 6 5 电子技术专业英语教程 14 ANDoperation TheANDoperationfortwovariablesAandBgeneratesaresultof1ifbothAandBare1 However ifeitherAorB orboth arezero thentheresultis0 Thedotand symbolarebothusedtorepresenttheANDoperation TheANDoperationbetweentwobinarydigitsis0 0 00 1 01 0 01 1 1 2020 6 5 电子技术专业英语教程 15 ANDoperation TruthtableandSymbolicofNOTgate ThetruthtablefortheANDoperationisFigure19 6ANDgate 2020 6 5 电子技术专业英语教程 16 ANDOperation DiodeORgate AswedidfortheORgate letusassumethattherange0to 2Vrepresentslogic0andtherange3to5Vislogic1 Now ifAandBarebothHIGH say3 3V andtheanodeofbothdiodesat3 9V theswitchesinD1andD2close Acurrentflowsfrom 5VthroughresistorRto 3 3Vinputtoground TheoutputCwillbeHIGH 3 9V Ontheotherhand ifalowvoltage say0 5V isappliedatAandahighvoltage 3 3V isappliedatB ThevalueofRisselectedinsuchawaythat1 1VappearsattheanodesideofD1atthesametime3 9VappearsattheanodesideofD2 Acurrentflowsfromthe 5VinputthroughRandthediodestoground OutputCwillbelow 1 1V becausetheoutputwillbelowerofthetwovoltages Thus itcanbeshownthatwheneitheroneorbothinputsarelow theoutputislow sothecircuitworksasanANDgate Figure19 7DiodeANDgate 2020 6 5 电子技术专业英语教程 17 ANDOperation Example The74HC08 or74LS08 isacommerciallyavailablequad2 input14 pinANDgatechip Thischipcontainsfour2 input l outputindependentANDgatesasshowninFigure19 8 Figure19 8Pindiagramfor74HC08or74LS08 74LS08