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1、英文资料及中文翻译FLIP-FLOPS1IntorduceInthispassage,weshowhowtodesignflip-flops,whichoperateasone-bitmemorycells.Flip-flopsarealsocalledlatches.Logiccircuitsconstructedusingflip-flopscanhavethepresentoutputbeafunctionofboththepastandpresentinputs.Suchcircuitsarecall
2、edsenfientiallogiccircuits.Allflip-flopsarebasedonthesameprinciple:Positivefeedbackisusedtoproduceacircuitthatisbistable.Abistablecircuitisonethathastwostableoperatingpoints.Whichoperatingpointthecircuitisiniscalledthestateofthecircuit.Ifthestatecanbesensed
3、andchanged,thenthecircuitcanfunctionasaone-bitmemoryelement.ThesimplestbistablecircuitisconstructedusingtwoinvertersinaloopasshowninFigure1－1.Thiscircuitonlyhastwonodes,AandB.Becauseoftheinverters,ifAishigh,Bmustbelowandviceversa;hence,thecircuithastwostabl
4、estates.Theoperationofthebistablecircuitcanalsobeviewedusingaplotofthetransfercharacteristicofthetwoinvertersinseries,asshowninFigure1－2.Part(a)ofthefigureshowsthestatictransfercharacteristicofoneoftheinverters.Whentheinputvoltageisbelowthethreshold(alogica
5、lZERO),theoutputvoltageishigh(alogicalONE).Whentheinputvoltageisgreaterthanthethreshold,theoutputvoltageislow.Inpart(b)ofthefigure,weshowthetransfercharacteristicthatresultsfromputtingbothinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieo
6、nthischaracteristic.Becauseoftheexternalconnection,theinputandoutputvoltagesoftheseriesconnectionofthetwoinvertersmustbethesame.Therefore,wedrawalinewithaslopeofunityontheplotaswell.Thislineiscalledtheloadline,becauseitrepresentstheexternalloadconnectionfor
7、thetwoinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieontheloadline.Therefore,whentheequationsaresimultaneouslysolved,theonlypossibleoperatingpointsarefoundwherethestraightlineintersectsthetransfercharacteristic.Therearethreeintersection
8、sontheplot,butonlytwoofthemarestable,aswewillnowdemonstrate.Thepointwheretheloadlineintersectsthemiddleofthetransfercharacteristicisnotstable.Toseethatthisstatementistrue,supposeforthemomentthatthecirc
