keil c51中啟動代碼詳細說明

keilc51STARTUP.A51文件（默認設置）吧！根據(jù)源文件中的說明文字，我STARTUP.A51文件的工作方式和作用！讓我們把它先漢化一下看看！$NOMOD51;Ax51宏匯編器控制命令：預定義的;;ThisfileispartoftheC51Compiler;Copyright(c)1988-2002KeilElektronikGmbHandKeilSoftware,;;STARTUP.A51:ThiscodeisexecutedafterprocessorSTARTUP.A51STARTUP.A51;TotranslatethisfileuseA51withthefollowing 將按照下面令行語句調(diào)用A51編譯器進行編譯產(chǎn)生目標文 A51;;TolinkthemodifiedSTARTUP.OBJfiletoyourapplicationusethe;BL51 BL51,;;;User-definedPower-OnInitializationof;自定義上電后需要初始化的區(qū);WiththefollowingEQUstatementstheinitializationof;atprocessorresetcanbe;使用下列EQU偽指令定義初始化的區(qū)域在單片機復位后定義生 ;theabsolutestart-addressofIDATAmemoryisalways0 ;thelengthofIDATAmemoryinbytes.IDATA（間接尋址區(qū)）0；IDATALEN;IDATA區(qū)長度（以字節(jié)為單位 ;theabsolutestart-addressofXDATAmemory ;thelengthofXDATAmemoryinbytes.;XDATA（外部直接尋址區(qū)）XDATASTARTXDATA地;址XDATALEN用于指定需要初始化的XDATA區(qū)長度（以字節(jié)為單位）* ;theabsolutestart-addressofPDATAmemory ;thelengthofPDATAmemoryinbytes.;PDATA（頁尋址區(qū)）PDATASTARTPDATAPDATALEN用于指定需要初始化的;PDATA區(qū)長度（以字節(jié)為單位;Notes:TheIDATAspaceoverlapsphysicallytheDATAandBITareasof 8051CPU.Atminimumthememoryspaceoccupiedfromthe run-timeroutinesmustbesetto;注釋：8051IDATADATA（直接尋址區(qū)BIT區(qū)（位尋址區(qū)）。C51（庫）占用了最小;0;;;ReentrantStack;;ThefollowingEQUstatementsdefinethestackpointerfor;functionsandinitialized;EQU;StackSpaceforreentrantfunctionsintheSMALLSMALL ;setto1ifsmallreentrantis;如果再SMALL模式下使用重入則設為1 0FFH+1;settopofstacktohighestlocation+1.;設置堆棧頂最置;;StackSpaceforreentrantfunctionsintheLARGELARGE ;setto1iflargereentrantis;如果再LARGE模式下使用重入則設為1 0FFFFH+1;settopofstacktohighestlocation+1.;設置堆棧頂最置;;StackSpaceforreentrantfunctionsintheCOMPACT;COMPACT ;setto1ifcompactreentrantis;如果再COMPACT模式下使用重入則設為1 0FFFFH+1;settopofstacktohighestlocation+1.;設置堆棧頂最置;;;;PageDefinitionforUsingtheCompactModelwith64KBytexdata;COMPACT64KBXDATARAM;ThefollowingEQUstatementsdefinethexdatapageusedfor;variables.TheEQUPPAGEmustconformwiththePPAGEcontrol;inthelinker;EQUPDATAXDATA ;setto1ifpdataobjectare;PDATA; ;definePPAGE; ;SFRthatsuppermostaddress;(most8051variantsuseP2asuppermostaddress8051P2的最高地址字節(jié);;StandardSFR;SFR EXTRNCODEPUBLIC?C_STARTUP; ;code0地址處放以下代碼（AT指令進行絕對地址的定位 IFIDATALEN<>;1 R0,#IDATALEN-1 IFXDATALEN<>;1 R7,#LOWIF(LOW(XDATALEN))<>; R6,#(HIGH(XDATALEN))

R6,#HIGH IFPPAGEENABLE<> IFPDATALEN<>;1 R0,#LOW(PDATASTART) R7,#LOW(PDATALEN) IFIBPSTACK<>;SMALLEXTRNDATA ?C_IBP,#LOWIFXBPSTACK<>;COMPACTEXTRNDATA ?C_XBP,#HIGHXBPSTACKTOP ?C_XBP+1,#LOWXBPSTACKTOPIFPBPSTACK<>;LARGEEXTRNDATA ?C_PBP,#LOW ;Thi