SysTick_Config(uint32_t ticks);库函数是用来定义重装载值的,我们来看下它的详细信息。该库函数在在 core_cm3.h中被定义。
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 */
}
可以看出SysTick->的TICKINT位被配置为1,为1时倒计时数到 0 时产生 SysTick 异常请
求, 为0时倒计时数到 0 时无动作。我们只需要把SysTick_CTRL_TICKINT_Msk换成0就可以屏蔽掉SysTick中断服务函数
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 |
0|
SysTick_CTRL_ENABLE_Msk; /* Enable SysTick IRQ and SysTick Timer */
return (0); /* Function successful */
}