uCOS-II系统延时函数

延时函数的几点说明：

1.延时函数由两个OSTimeDly()和OSTimeDlyHMSM(),其实OSTimeDlyHMSM函数实现内部也是调用了OSTimeDly函数。

不同的地方是OSTimeDlyHMSM的参数多了几个参数，可以指定具体要延时几个小时、几分钟、几秒钟或几毫秒的时间。

2.这两个延时函数执行时，都会阻塞当前Task的执行，直到延时时间结束才可以进行往下执行该Task.

3. 由于延时函数会阻塞当前执行的任务，所以拿该延时函数来做定时任务的定时时间管理可能会不准确。

OSTimeDlyHMSM函数实现代码如下：

/*
*********************************************************************************************************
*                                     DELAY TASK FOR SPECIFIED TIME
*
* Description: This function is called to delay execution of the currently running task until some time
*              expires.  This call allows you to specify the delay time in HOURS, MINUTES, SECONDS and
*              MILLISECONDS instead of ticks.
*
* Arguments  : hours     specifies the number of hours that the task will be delayed (max. is 255)
*              minutes   specifies the number of minutes (max. 59)
*              seconds   specifies the number of seconds (max. 59)
*              milli     specifies the number of milliseconds (max. 999)
*
* Returns    : OS_ERR_NONE
*              OS_ERR_TIME_INVALID_MINUTES
*              OS_ERR_TIME_INVALID_SECONDS
*              OS_ERR_TIME_INVALID_MS
*              OS_ERR_TIME_ZERO_DLY
*              OS_ERR_TIME_DLY_ISR
*
* Note(s)    : The resolution on the milliseconds depends on the tick rate.  For example, you can't do
*              a 10 mS delay if the ticker interrupts every 100 mS.  In this case, the delay would be
*              set to 0.  The actual delay is rounded to the nearest tick.
*********************************************************************************************************
*/

#if OS_TIME_DLY_HMSM_EN > 0
INT8U  OSTimeDlyHMSM (INT8U hours, INT8U minutes, INT8U seconds, INT16U ms)
{
    INT32U ticks;
    INT16U loops;


    if (OSIntNesting > 0) {                      /* See if trying to call from an ISR                  */
        return (OS_ERR_TIME_DLY_ISR);
    }
#if OS_ARG_CHK_EN > 0
    if (hours == 0) {
        if (minutes == 0) {
            if (seconds == 0) {
                if (ms == 0) {
                    return (OS_ERR_TIME_ZERO_DLY);
                }
            }
        }
    }
    if (minutes > 59) {
        return (OS_ERR_TIME_INVALID_MINUTES);    /* Validate arguments to be within range              */
    }
    if (seconds > 59) {
        return (OS_ERR_TIME_INVALID_SECONDS);
    }
    if (ms > 999) {
        return (OS_ERR_TIME_INVALID_MS);
    }
#endif
                                                 /* Compute the total number of clock ticks required.. */
                                                 /* .. (rounded to the nearest tick)                   */
    ticks = ((INT32U)hours * 3600L + (INT32U)minutes * 60L + (INT32U)seconds) * OS_TICKS_PER_SEC
          + OS_TICKS_PER_SEC * ((INT32U)ms + 500L / OS_TICKS_PER_SEC) / 1000L;
    loops = (INT16U)(ticks >> 16);               /* Compute the integral number of 65536 tick delays   */
    ticks = ticks & 0xFFFFL;                     /* Obtain  the fractional number of ticks             */
    OSTimeDly((INT16U)ticks);
    while (loops > 0) {
        OSTimeDly((INT16U)32768u);
        OSTimeDly((INT16U)32768u);
        loops--;
    }
    return (OS_ERR_NONE);
}

OSTimeDly函数代码实现如下：

/*
*********************************************************************************************************
*                                DELAY TASK 'n' TICKS   (n from 0 to 65535)
*
* Description: This function is called to delay execution of the currently running task until the
*              specified number of system ticks expires.  This, of course, directly equates to delaying
*              the current task for some time to expire.  No delay will result If the specified delay is
*              0.  If the specified delay is greater than 0 then, a context switch will result.
*
* Arguments  : ticks     is the time delay that the task will be suspended in number of clock 'ticks'.
*                        Note that by specifying 0, the task will not be delayed.
*
* Returns    : none
*********************************************************************************************************
*/

void  OSTimeDly (INT16U ticks)
{
    INT8U      y;
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr = 0;
#endif



    if (OSIntNesting > 0) {                      /* See if trying to call from an ISR                  */
        return;
    }
    if (ticks > 0) {                             /* 0 means no delay!                                  */
        OS_ENTER_CRITICAL();
        y            =  OSTCBCur->OSTCBY;        /* Delay current task                                 */
        OSRdyTbl[y] &= ~OSTCBCur->OSTCBBitX;
        if (OSRdyTbl[y] == 0) {
            OSRdyGrp &= ~OSTCBCur->OSTCBBitY;
        }
        OSTCBCur->OSTCBDly = ticks;              /* Load ticks in TCB                                  */
        OS_EXIT_CRITICAL();
        OS_Sched();                              /* Find next task to run!                             */
    }
}

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