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1、英文资料及中文翻译FLIP-FLOPS1IntorduceInthispassage,weshowhowtodesignflip-flops,whichoperateasone-bitmemorycells.Flip-flopsarealsocalledlatches.Logiccircuitsconstructedusingflip-flopscanhavethepresentoutputbeafunctionofboththepastandpresentinputs.Suchcircuitsarecalledsenf
2、ientiallogiccircuits.Allflip-flopsarebasedonthesameprinciple:Positivefeedbackisusedtoproduceacircuitthatisbistable.Abistablecircuitisonethathastwostableoperatingpoints.Whichoperatingpointthecircuitisiniscalledthestateofthecircuit.Ifthestatecanbesensedandchanged,t
3、henthecircuitcanfunctionasaone-bitmemoryelement.ThesimplestbistablecircuitisconstructedusingtwoinvertersinaloopasshowninFigure1－1.Thiscircuitonlyhastwonodes,AandB.Becauseoftheinverters,ifAishigh,Bmustbelowandviceversa;hence,thecircuithastwostablestates.Theoperati
4、onofthebistablecircuitcanalsobeviewedusingaplotofthetransfercharacteristicofthetwoinvertersinseries,asshowninFigure1－2.Part(a)ofthefigureshowsthestatictransfercharacteristicofoneoftheinverters.Whentheinputvoltageisbelowthethreshold(alogicalZERO),theoutputvoltagei
5、shigh(alogicalONE).Whentheinputvoltageisgreaterthanthethreshold,theoutputvoltageislow.Inpart(b)ofthefigure,weshowthetransfercharacteristicthatresultsfromputtingbothinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieonthischaracteristic.Becauseoft
6、heexternalconnection,theinputandoutputvoltagesoftheseriesconnectionofthetwoinvertersmustbethesame.Therefore,wedrawalinewithaslopeofunityontheplotaswell.Thislineiscalledtheloadline,becauseitrepresentstheexternalloadconnectionforthetwoinvertersinseries.Anysolutiono
7、ftheequationsforthiscircuitmustalsolieontheloadline.Therefore,whentheequationsaresimultaneouslysolved,theonlypossibleoperatingpointsarefoundwherethestraightlineintersectsthetransfercharacteristic.Therearethreeintersectionsontheplot,butonlytwoofthemarestable,aswew
8、illnowdemonstrate.Thepointwheretheloadlineintersectsthemiddleofthetransfercharacteristicisnotstable.Toseethatthisstatementistrue,supposeforthemomentthatthecirc
