os_cpu_c.c

s3c2410上用Keil开发的ucosII源代码

在本移植中就是这么作的。用#define语句定义的常数OS_CPU_HOOKS_EN(见OS_CFG.H)应该置为1.该函数由OSTaskCreate()或  
OSTaskCreateExt()调用，用来初始化任务堆栈。将堆栈的结构初始化成看起来好像刚刚发生过中断一样，处理器的所有寄存器被推入堆栈。  
当调用OSTaskCreate()或OSTaskCreateExt()建立一个新任务时，须传递的参数是：任务代码的起始地址(task),参数指针(pdata),任务堆栈  
顶端的地址(ptos)以及任务的优先级(prio).OSTaskCreateExt()还需要一些其他参数，但与OSTaskStkInit()没有关系。为了合理地初始化  
堆栈结构，OSTaskStkInit()只需要以上提到的前三个参数(task,pdata,ptos)。关于opt是调用OSTaskStkInit()函数时须要传递过去的参数  
。因为只有OSTaskCreate()函数不支持附加的opt选项，因此，当OSTaskCreate()调用OSTaskStkInit()时，将opt设置为0x0000.  
*  
* Description: This function is called by either OSTaskCreate() or OSTaskCreateExt() to initialize the  
*              stack frame of the task being created.  This function is highly processor specific.  
*  
* Arguments  : task          is a pointer to the task code  
*  
*              pdata         is a pointer to a user supplied data area that will be passed to the task  
*                            when the task first executes.  
*  
*              ptos          is a pointer to the top of stack.  It is assumed that 'ptos' points to  
*                            a 'free' entry on the task stack.  If OS_STK_GROWTH is set to 1 then   
*                            'ptos' will contain the HIGHEST valid address of the stack.  Similarly, if  
*                            OS_STK_GROWTH is set to 0, the 'ptos' will contains the LOWEST valid address  
*                            of the stack.  
*  
*              opt           specifies options that can be used to alter the behavior of OSTaskStkInit().  
*                            (see uCOS_II.H for OS_TASK_OPT_???).  
*  
* Returns    : Always returns the location of the new top-of-stack' once the processor registers have  
*              been placed on the stack in the proper order.  
*  
* Note(s)    : Interrupts are enabled when your task starts executing. You can change this by setting the  
*              PSW to 0x0002 instead.  In this case, interrupts would be disabled upon task startup.  The  
*              application code would be responsible for enabling interrupts at the beginning of the task  
*              code.  You will need to modify OSTaskIdle() and OSTaskStat() so that they enable   
*              interrupts.  Failure to do this will make your system crash!  
*********************************************************************************************************  
*/   
   
OS_STK  *OSTaskStkInit (void (*task)(void *pd), void *pdata, OS_STK *ptos, INT16U opt)   
{   
    //INT16U
	OS_STK *stk;   
	(void)opt;   // opt    = opt;//'opt' is not used, prevent warning 
	stk = ptos;  //stk = (INT16U *)ptos; // Load stack pointer   

	//The task received an optional argument ‘p_arg’. That’s why ‘p_arg’ is passed in R0 when the task is created. 
	//The initial value of most of the CPU registers is not important so, we decided to initialize them to values 
	//corresponding to their register number. This makes it convenient when debugging and examining stacks in RAM. 
	//The initial values are thus useful when the task is first created but, of course, the register values will most 
	//likely change as the task code is executed.

	//代码取决于堆栈的结构。
	// Registers stacked as if saved on exception 
	/*
	*(stk) = (INT32U)0x01000000L;   // xPSR 
	*(--stk) = (INT32U)task;        // Entry Point 
	*(--stk) = (INT32U)0xFFFFFFFEL; // R14 (LR) 
	*(--stk) = (INT32U)0x12121212L; // R12 
	*(--stk) = (INT32U)0x03030303L; // R3 
	*(--stk) = (INT32U)0x02020202L; // R2 
	*(--stk) = (INT32U)0x01010101L; // R1 
	*(--stk) = (INT32U)pdata; // R0 : argument 

	// Remaining registers saved on process stack 
	*(--stk) = (INT32U)0x11111111L; // R11 
	*(--stk) = (INT32U)0x10101010L; // R10 
	*(--stk) = (INT32U)0x09090909L; // R9 
	*(--stk) = (INT32U)0x08080808L; // R8 
	*(--stk) = (INT32U)0x07070707L; // R7 
	*(--stk) = (INT32U)0x06060606L; // R6 
	*(--stk) = (INT32U)0x05050505L; // R5 
	*(--stk) = (INT32U)0x04040404L; // R4 
	*/
	
	*(stk) = (INT32U)task;        // PC, Entry Point, the code will return immediately to the task when this pops up.
	*(--stk) = (INT32U)task;        // LR, R14 
	*(--stk) = (INT32U)0x12121212L; // R12 
	*(--stk) = (INT32U)0x11111111L; // R11 
	*(--stk) = (INT32U)0x10101010L; // R10 
	*(--stk) = (INT32U)0x09090909L; // R9 
	*(--stk) = (INT32U)0x08080808L; // R8 
	*(--stk) = (INT32U)0x07070707L; // R7 
	*(--stk) = (INT32U)0x06060606L; // R6 
	*(--stk) = (INT32U)0x05050505L; // R5 
	*(--stk) = (INT32U)0x04040404L; // R4 
	*(--stk) = (INT32U)0x03030303L; // R3 
	*(--stk) = (INT32U)0x02020202L; // R2 
	*(--stk) = (INT32U)0x01010101L; // R1 
	*(--stk) = (INT32U)pdata; // R0 : argument 
	*(--stk) =  (INT32U)0x01000000L;  // xPSR //(INT32U)task;  

    return ((OS_STK *)stk);    
	// 堆栈初始化工作结束后，OSTaskStkInit()函数返回新的堆栈栈顶指针，OSTaskCreate()  
    // 或OSTaskCreateExt()将指针保存在任务的控制块OS_TCB中。
}

/*$PAGE*/
/*********************************************************************************************************
*                                           TASK SWITCH HOOK  
*  
* Description: This function is called when a task switch is performed.  This allows you to perform other  
*              operations during a context switch.作任务切换时，会调用OSTaskSwHook()函数。不管任务切换是通过OSCtxSw()函数  
实现的，还是通过OSIntCtxSw()函数(见OS_CPU_A.ASM)实现的，都会调用该函数。OSTaskSwHook()可以直接访问OSTCBCur和OSTCBHighRdy这  
2个全局变量。OSTCBCur指向被切换出去的任务的任务控制块，而OSTCBHighRdy指向新任务的任务控制块。注意：在调用OSTaskSwHook()期  
间，中断一直是关掉的。因此附加代码会影响中断的响应时间，所以尽量使这部分代码减至最少。  
*  
* Arguments  : none  
*  
* Note(s)    : 1) Interrupts are disabled during this call.  
*              2) It is assumed that the global pointer 'OSTCBHighRdy' points to the TCB of the task that  
*                 will be 'switched in' (i.e. the highest priority task) and, 'OSTCBCur' points to the   
*                 task being switched out (i.e. the preempted task).  
**********************************************************************************************************  
*/
#if OS_CPU_HOOKS_EN > 0 
void  OSTaskSwHook (void)   
{   
}   
#endif    
   
/*  
*********************************************************************************************************  
*                                           OSTCBInit() HOOK  
*  
* Description: This function is called by OS_TCBInit() after setting up most of the TCB.OS_TCBInit()函数在调用  
OSTaskCreateHook()之前，会先调用OSTCBInitHook()函数中做一些与初始化控制块OS_TCB有关的处理；在OSTaskCreateHook()中做一些与  
初始化任务有关的处理。是否用OSTaskCreateHook()和OSTCBInitHook()函数，完全取决于用户。同OSTaskCreateHook()一样，  
OSTCBInitHook()会收到指向新添加任务的任务控制块的指针，而这个新添加任务的任务控制块绝大部分已经初始化完成，但是还没有链接  
到已经建立任务的链表中。详见OS_TCBInit()。  
*  
* Arguments  : ptcb    is a pointer to the TCB of the task being created.  
*  
* Note(s)    : 1) Interrupts may or may not be ENABLED during this call.  
*********************************************************************************************************  
*/   
#if OS_CPU_HOOKS_EN > 0 && OS_VERSION > 203    
void  OSTCBInitHook (OS_TCB *ptcb)   
{   
    ptcb = ptcb;                                           /* Prevent Compiler warning                 */   
}   
#endif    
   
   
/*  
*********************************************************************************************************  
*                                               TICK HOOK  
*  
* Description: This function is called every tick.OSTimeTickHook()函数在每个时钟节拍都会被OSTimeTick()调用。实际上，  
OSTimeTickHook()是在UCOS真正处理时钟节拍之前被调用的，以便于用户能先处理应急的事务。  
*  
* Arguments  : none  
*  
* Note(s)    : 1) Interrupts may or may not be ENABLED during this call.  
*********************************************************************************************************  
*/   
#if OS_CPU_HOOKS_EN > 0     
void  OSTimeTickHook (void)   
{   
}   
#endif