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1、英文资料及中文翻译FLIP-FLOPS1IntorduceInthispassage,weshowhowtodesignflip-flops,whichoperateasone-bitmemorycells.Flip-flopsarealsocalledlatches.Logiccircuitsconstructedusingflip-flopscanhavethepresentoutputbeafunctionofboththepastandpresentinputs.Suchcircuitsarecalledsenfient
2、iallogiccircuits.Allflip-flopsarebasedonthesameprinciple:Positivefeedbackisusedtoproduceacircuitthatisbistable.Abistablecircuitisonethathastwostableoperatingpoints.Whichoperatingpointthecircuitisiniscalledthestateofthecircuit.Ifthestatecanbesensedandchanged,thentheci
3、rcuitcanfunctionasaone-bitmemoryelement.ThesimplestbistablecircuitisconstructedusingtwoinvertersinaloopasshowninFigure1－1.Thiscircuitonlyhastwonodes,AandB.Becauseoftheinverters,ifAishigh,Bmustbelowandviceversa;hence,thecircuithastwostablestates.Theoperationofthebista
4、blecircuitcanalsobeviewedusingaplotofthetransfercharacteristicofthetwoinvertersinseries,asshowninFigure1－2.Part(a)ofthefigureshowsthestatictransfercharacteristicofoneoftheinverters.Whentheinputvoltageisbelowthethreshold(alogicalZERO),theoutputvoltageishigh(alogicalON
5、E).Whentheinputvoltageisgreaterthanthethreshold,theoutputvoltageislow.Inpart(b)ofthefigure,weshowthetransfercharacteristicthatresultsfromputtingbothinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieonthischaracteristic.Becauseoftheexternalconnection
6、,theinputandoutputvoltagesoftheseriesconnectionofthetwoinvertersmustbethesame.Therefore,wedrawalinewithaslopeofunityontheplotaswell.Thislineiscalledtheloadline,becauseitrepresentstheexternalloadconnectionforthetwoinvertersinseries.Anysolutionoftheequationsforthiscirc
7、uitmustalsolieontheloadline.Therefore,whentheequationsaresimultaneouslysolved,theonlypossibleoperatingpointsarefoundwherethestraightlineintersectsthetransfercharacteristic.Therearethreeintersectionsontheplot,butonlytwoofthemarestable,aswewillnowdemonstrate.Thepointwh
8、eretheloadlineintersectsthemiddleofthetransfercharacteristicisnotstable.Toseethatthisstatementistrue,supposeforthemomentthatthecirc
