Freescale 高级S12系列单片机编程.pdf

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1、AdvancedCprogrammingfor16-bitMCUsAustin,Texas25-29September,2006TMFreescale™andtheFreescalelogoaretrademarksofFreescaleSemiconductor,Inc.Allotherproductorservicenamesarethepropertyoftheirrespectiveowners.©FreescaleSemiconductor,Inc.2006.1IntroductionWhatisthistrai

2、ningabout?TMAgenda•MemoryModels•Optimizingfunctionscallsbyhand•RunningroutinesinRAM•RunningafunctionfromtheStackFreescale™andtheFreescalelogoaretrademarksofFreescaleSemiconductor,Inc.AllotherproductorservicenamesareTMthepropertyoftheirrespectiveowners.©FreescaleSe

3、miconductor,Inc.2006.3MemoryModelsModels!Where?TMWhatisamemorymodel?MemoryModelsAmemorymodelisasetofrulesthatchangesthedefaultbehaviorofthecompiler.Ittellsthecompilerwhatinstructionstogeneratewhenaccessingdataandcallingfunctions.TheCompilerforthe16bitsMCU’ssupport

4、sthreedifferentmemorymodels.•SMALL(codeanddatafitin64Kb)
Dataandfunctionsareaccessedbydefaultwith16bitaddresses.•BANKED(codeinbankedmemory)
Dataisalsoaccessedwith16bitaddresses,functionsarecalledusingbankedcalls•LARGE(Suitedwhenusingbothcodeanddatainbankedmemory)

5、bothcodeanddataareaccessedusingpagedconventionsBecareful,Thiscausesgreatoverhead.Freescale™andtheFreescalelogoaretrademarksofFreescaleSemiconductor,Inc.AllotherproductorservicenamesareTMthepropertyoftheirrespectiveowners.©FreescaleSemiconductor,Inc.2006.5MemoryMod

6、elsDifferenceswhencallingbankedandnon-bankedfunctionsIfafunctionisinbankedmemory,ithastobecalleddifferentlythanafunctioninnon–bankedmemory.Inparticular:1.ThecurrentPPAGEpagenumberhastobesaved2.Thecalledfunction’spagenumberhastobewrittentothePPAGEregister3.Thefunct

7、ionhastobecalled.4.Whenthefunctionreturns,thePPAGEvaluehastoberestored.Acalltoabankedfunctionismoreexpensivebothincodesizeandexecutiontime.Freescale™andtheFreescalelogoaretrademarksofFreescaleSemiconductor,Inc.AllotherproductorservicenamesareTMthepropertyoftheirre

8、spectiveowners.©FreescaleSemiconductor,Inc.2006.6ComparisonbetweenmemorymodelsLet’scomparetheassemblyinstructionsgeneratedbythecompilerwiththefollowings