/**
* [url=home.php?mod=space&uid=247401]@brief[/url] This function execute long delay function.
* @param[in] us Delay time.
* [url=home.php?mod=space&uid=266161]@return[/url] None
* [url=home.php?mod=space&uid=1543424]@Details[/url] Use the SysTick to generate the long delay time and the UNIT is in us.
* The SysTick clock source is from HCLK, i.e the same as system core clock.
* User can use SystemCoreClockUpdate() to calculate CyclesPerUs automatically before using this function.
*/
__STATIC_INLINE void CLK_SysTickLongDelay(uint32_t us)
{
uint32_t delay;
/* It should <= 335544us for each delay loop */
delay = 335544UL;
do
{
if(us > delay)
{
us -= delay;
}
else
{
delay = us;
us = 0UL;
}
SysTick->LOAD = delay * CyclesPerUs;
SysTick->VAL = (0x0UL);
SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk;
/* Waiting for down-count to zero */
while((SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk) == 0UL);
/* Disable SysTick counter */
SysTick->CTRL = 0UL;
}while(us > 0UL);
}
do
{
if(us > delay)
{
us -= delay;
}
else
{
delay = us;
us = 0UL;
}
实现了任意数值的延时。当大于最大限制时候，就先执行限制，并扣掉该值，循环，直到小于最大计量。
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