chap04-embedded_processors .pdf

《chap04-embedded_processors .pdf》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、CHAPTER4EmbeddedProcessorsInThisChapterÑWhatanISAisandwhatitdefinesÑDiscussionoftheinternalprocessordesignasrelatedtothevonNeumannmodelÑIntroductiontoprocessorperformanceProcessorsarethemainfunctionalunitsofanembeddedboard,andareprimarilyresponsibleforproces

2、singinstructionsanddata.Anelectronicdevicecontainsatleastonemasterproces-sor,actingasthecentralcontrollingdevice,andcanhaveadditionalslaveprocessorsthatworkwithandarecontrolledbythemasterprocessor.Theseslaveprocessorsmayeitherextendtheinstructionsetofthemaster

3、processororacttomanagememory,buses,andI/O(input/output)devices.Intheblockdiagramofanx86referenceboard,showninFigure4-1,theAtlasSTPCisthemasterprocessor,andthesuperI/Oandethernetcontrollersareslaveprocessors.SDRAMCPUPCIBusto(SODIMM)CoreBaseboardCRT/TFTtoSTPC®At

4、lasIDEtoBaseboard(ComputerBaseboardInaChip)KeyboardEthernet&MousetoControllerBaseboardHost-PeripheralSerialPortsInterfaceUSB(4)toToBaseboardBaseboardInternalBusRealTimeClock(RTC)Parallel/FloppytoBaseboardSuperI/OBIOSControllerInfraredtoBaseboardFigure4-1:Ampro

5、’sEncore400board[4-1]129Chapter4AsshowninFigure4-1,embeddedboardsaredesignedaroundthemasterprocessor.Thecomplexityofthemasterprocessorusuallydetermineswhetheritisclassifiedasamicro-processororamicrocontroller.Traditionally,microprocessorscontainaminimalsetofint

6、egratedmemoryandI/Ocomponents,whereasmicrocontrollershavemostofthesys-temmemoryandI/Ocomponentsintegratedonthechip.However,keepinmindthatthesetraditionaldefinitionsmaynotstrictlyapplytorecentprocessordesigns.Forexample,micro-processorsareincreasinglybecomingmor

7、eintegrated.WhyUseanIntegratedProcessor?Whilesomecomponents,likeI/O,mayshowadecreaseinperformancewhenintegratedintoamasterprocessorasopposedtoremainingadedicatedslavechip,manyothersshowanincreaseinperformancebecausetheynolongerhavetodealwiththelatenciesinvolve

8、dwithtransmittingdataoverbusesbetweenprocessors.Anintegratedprocessoralsosimplifiestheentireboarddesignsincetherearefewerboardcomponents,resultinginaboardthatissimplertodebug(fewerp