关于《STM32库开发实战指南》中SysTick中断优先级的疑问

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楼主 | 2019-11-13 18:44 | 只看该作者回帖奖励

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systick, STM32, 中断优先级, IO, rio

static __INLINE uint32_t SysTick_Config(uint32_t ticks)
{
  if (ticks > SysTick_LOAD_RELOAD_Msk)  return (1);          /* Reload value impossible */

  SysTick->LOAD  = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;    /* set reload register */
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);  /* set Priority for Cortex-M0 System Interrupts */
  SysTick->VAL = 0;                                        /* Load the SysTick Counter Value */
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk |
               SysTick_CTRL_TICKINT_Msk |
               SysTick_CTRL_ENABLE_Msk;                   /* Enable SysTick IRQ and SysTick Timer */
  return (0);                                                 /* Function successful */

}这个是systick的配置函数，查看了SysTick_IRQn为-1，NVIC_PRIO_BITS为4，请问大家，经过下面这个函数后，优先级到底是什么？应该是比所有的外设的中断优先级都要高吧(SysTick_IRQn为-1，负数！）

static __INLINE void NVIC_SetPriority(IRQn_Type IRQn, uint32_t priority)
{
  if(IRQn < 0) {
SCB->SHP[((uint32_t)(IRQn) & 0xF)-4] = ((priority << (8 - __NVIC_PRIO_BITS)) & 0xff); } /* set Priority for Cortex-M3 System Interrupts */
  else {
NVIC->IP[(uint32_t)(IRQn)] = ((priority << (8 - __NVIC_PRIO_BITS)) & 0xff); }       /* set Priority for device specific Interrupts  */
}这个是设置systick中断的库函数

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