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1、外文翻译SerialMemoriesOverviewManyofusliketousesmall,singlechipmicrocontrollers.Theyarerelativelycheap,easytowireuptomakerun,andoveralljustmightyconvenienttouse.Onedownsidetousingthesesinglechipcontrollersisthelackoflargeamountsofmemory.Sure,youcanhookupexternalmemorytomostofthem,butthatrequire
2、salotofwork,andusuallyconsumesothervaluableresources,mainlytheI/Opinsthatmakethechipuseful.Thereishelpoutthere!Thereareseveralformsofmemorythatdon'trequirethestandardaddressbusanddatabuswiring.Thesememoriesarecalledserialmemories,andtheyarejustthetickettoallowyoutostorelargeamountsofinforma
3、tionwithoutgivingupthosepreciousI/Olines.ThereareseveraldifferentstylesofserialEEPROM.ThefocusofthisarticleisgoingtobeSPIbaseddevices.Therearealso1,2,and3wireserialEEPROMdevicesthatfunctioninasimilarway,buthavedifferentinterfacelogic.Thisarticleisgoingtointroducethebasicsofserialmemories,an
4、dpresentthedriversoftwareneededtomakeitoperate.MissingtheBusThebigadvantagetousingaSerialEEPROMisthatthewiringonlyrequires4signallinesfromtheCPUtooperateit.Comparethiswithamorestandardmemory,whichrequiresanaddressbusandadatabus!TheamountofgluelogicrequiredtomakeaSerialEEPROMoperateisextreme
5、lylow.Forexample,checkoutthefollowingtwopackages.Atraditionalmemory,suchasa27256,requiresa28-pinparttobewiredintoyourcircuit.Thereare15addresslines,8outputlines,plusassortedcontrollines.Ontheotherhand,aserialEEPROMcanbepurchasedusingina8-pinpackage.Thereis1inputline,1outputline,1controlline
6、,and1clocklinerequired.Thereareacoupleofothercontrollinesavailable,butarenotactuallyrequiredifyouwishtoavoidthem.Asyoucanimagine,thesepartsaloteasiertowirein,muchsmallerandbestofallaremightycheap! An8kx8partcostsabout$1.61atDigkey.Ofcourse,therearetradeoffs.SincethememoryoftheserialEEPROMis
7、accessedonebitatatime,thereisaspeedpenaltytobepaid.However,thesearestillextremelyfastparts.Theycanoutputtheirdataatover2millionbitspersecond,whichisquitereasonableformanyapplications.So,forasmallamountofsoftwareoverheadandonly4I/Opins,youcanhaveyourselfs
