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1、英文资料及中文翻译FLIP-FLOPS1IntorduceInthispassage,weshowhowtodesignflip-flops,whichoperateasone-bitmemorycells.Flip-flopsarealsocalledlatches.Logiccircuitsconstructedusingflip-flopscanhavethepresentoutputbeafunctionofboththepastandpresentinputs.Suchcircuitsarecalledsenfientiallogiccircuits.Allfl
2、ip-flopsarebasedonthesameprinciple:Positivefeedbackisusedtoproduceacircuitthatisbistable.Abistablecircuitisonethathastwostableoperatingpoints.Whichoperatingpointthecircuitisiniscalledthestateofthecircuit.Ifthestatecanbesensedandchanged,thenthecircuitcanfunctionasaone-bitmemoryelement.Thes
3、implestbistablecircuitisconstructedusingtwoinvertersinaloopasshowninFigure1－1.Thiscircuitonlyhastwonodes,AandB.Becauseoftheinverters,ifAishigh,Bmustbelowandviceversa;hence,thecircuithastwostablestates.Theoperationofthebistablecircuitcanalsobeviewedusingaplotofthetransfercharacteristicofth
4、etwoinvertersinseries,asshowninFigure1－2.Part(a)ofthefigureshowsthestatictransfercharacteristicofoneoftheinverters.Whentheinputvoltageisbelowthethreshold(alogicalZERO),theoutputvoltageishigh(alogicalONE).Whentheinputvoltageisgreaterthanthethreshold,theoutputvoltageislow.Inpart(b)ofthefigu
5、re,weshowthetransfercharacteristicthatresultsfromputtingbothinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieonthischaracteristic.Becauseoftheexternalconnection,theinputandoutputvoltagesoftheseriesconnectionofthetwoinvertersmustbethesame.Therefore,wedrawalinewithaslopeo
6、funityontheplotaswell.Thislineiscalledtheloadline,becauseitrepresentstheexternalloadconnectionforthetwoinvertersinseries.Anysolutionoftheequationsforthiscircuitmustalsolieontheloadline.Therefore,whentheequationsaresimultaneouslysolved,theonlypossibleoperatingpointsarefoundwherethestraight
7、lineintersectsthetransfercharacteristic.Therearethreeintersectionsontheplot,butonlytwoofthemarestable,aswewillnowdemonstrate.Thepointwheretheloadlineintersectsthemiddleofthetransfercharacteristicisnotstable.Toseethatthisstatementistrue,supposeforthemomentthatthecirc
