ARM Macro Assembler    Page 1 


    1 00000000         ;*******************************************************
                       ************************************
    2 00000000         ;OS_CPU_A.s
    3 00000000         
    4 00000000         
    5 00000000         
    6 00000000                 PRESERVE8
    7 00000000                 AREA    OS_CPU_A, CODE, READONLY
    8 00000000                 CODE32
    9 00000000         
   10 00000000         ; 定義于ucos_ii.h中的外部變量
   11 00000000         ;OS_EXT  OS_TCB           *OSTCBCur;                    
                           /* Pointer to currently running TCB         */
   12 00000000         ;OS_EXT  OS_TCB           *OSTCBHighRdy;                
                           /* Pointer to highest priority TCB R-to-R   */
   13 00000000         ;OS_EXT  INT8U             OSPrioCur;                   
                           /* Priority of current task                 */
   14 00000000         ;OS_EXT  INT8U             OSPrioHighRdy;               
                           /* Priority of highest priority task        */
   15 00000000         ;OS_EXT  BOOLEAN           OSRunning;                   
                           /* Flag indicating that kernel is running   */
   16 00000000         
   17 00000000                 IMPORT  OSTCBCur
   18 00000000                 IMPORT  OSTCBHighRdy
   19 00000000         
   20 00000000                 IMPORT  OSPrioCur
   21 00000000                 IMPORT  OSPrioHighRdy
   22 00000000         
   23 00000000                 IMPORT  OSRunning
   24 00000000         
   25 00000000         ;*******************************************************
                       ************************************
   26 00000000                 EXPORT  OSStartHighRdy
   27 00000000         ;功能:       
   28 00000000         ;1)SP=OSTCBHighRdy->OSTCBStkPtr
   29 00000000         ;2)OSTCBCur->OSTCBHighRdy
   30 00000000         ;3)將當前優先級最高的任務切換到運行態,本任務只在系統開始
                       運行前運行一次!該函數不會返回到
   31 00000000         ;  調用者OSStart().
   32 00000000         
   33 00000000         OSStartHighRdy
   34 00000000 E59F40C8        LDR     r4,=OSRunning 
                                                   ;起始狀態時OSRunning顯然為0
   35 00000004 E3A05001        MOV     r5,#1
   36 00000008 E5C45000        STRB    r5,[r4]     ;直接置1,標志系統進入運行狀