微机原理ch06 memory and memory interfacing

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1、6MEMORYANDMEMORYINTERFACING6.1SEMICONDUCTORMEMORYFUNDAMENTALSInthedesignofallcomputers,semiconductormemoriesareusedasprimarystorageforcodeanddata.SemiconductormemoriesareconnecteddirectlytotheCPUandtheyarethememorythattheCPUfirstasksforinformation(codeanddata).Forthisreason,semiconductormemo

2、riesarereferredtoasprimarymemory.6.1.1MemorycapacityThenumberofbitsthatasemiconductormemorychipcanstoreiscalleditschipcapacity.ItcanbeinunitsofKbits(kilobits),Mbits(megabits),andsoon.Thismustbedistinguishedfromthestoragecapacityofcomputers.WhilethememorycapacityofamemoryICchipisalwaysgivenin

3、bits,thememorycapacityofacomputerisgiveninbytes.6.1.2MemoryorganizationMemorychipsareorganizedintoanumberoflocationswithintheIC.Eachlocationcanhold1bit,4bits,8bits,oreven16bits,dependingonhowitisdesignedinternally.Thenumberofbitsthateachlocationwithinthememorychipcanholdisalwaysequaltothenum

4、berofdatapinsonthechip.Howmanylocationsexistsinsideamemorychipdependsonthenumberofaddresspins.ThenumberoflocationswithinamemoryICalwaysequals2xwherexisthenumberofaddresspins.Therefore,thetotalnumberofbitsthatamemorychipcanstoreisequaltothenumberoflocationstimesthenumberofdatabitperlocation.T

5、osummary:1)Eachmemorychipcontains2xlocations,wherexisthenumberofaddresspinsonthechip.2)Eachlocationcontainsybits,whereyisthenumberofdatapinsonthechip.3)Theentirechipwillcontain2x×ybits,wherexisthenumberofaddresspinsonthechipandyisthenumberofdatapinsonthechip.4)The2x×yisreferredtoastheorganiz

6、ationofthememorychip,wherexisthenumberofaddresspinsonthechipandyisthenumberofdatapinsonthechip.5)For2x,use表61togivethenumberoflocationsinKorMunits.表61Powersof2x2x101K112K124K138K1416K1532K1664K17128K18256K19512K201M212M224M238M2416M324GExample1Agivenmemorychiphas12addresspinsand8datapins.F

7、ind:1)theorganization2)thecapacitySolution:1)Thismemorychiphas4096locations(212=4096),andeachlocationcanhold8bitsofdata.Thisorganizationof4096×8,oftenrepresentedas4K×8.2)Thecapacityisequalto32Kbitssincethereisatotalof4Klocationsandeachlocationscanh