SysTick初始化分析
//SysTick_Init(); /* SysTick初始化，配置为系统时钟 */
//运行系统时钟初始化函数：
void SysTick_Init(void)
{
if(SysTick_Config(SystemCoreClock / SYS_DIV) )//SysTick_Config系统时钟配置函数运行，计算=（系统时钟 / 分频系数）
{
while(1)
{
;
}
}
}
//SysTick_Config系统时钟配置函数，位置：core_cm3.h
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 */
}
//SystemCoreClock参数位置，SystemCoreClock（system_stm32f10x.c）
#ifdef SYSCLK_FREQ_HSE
uint32_t SystemCoreClock = SYSCLK_FREQ_HSE; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_24MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_24MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_36MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_36MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_48MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_48MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_56MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_56MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_72MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_72MHz; /*!< System Clock Frequency (Core Clock) */
#else /*!< HSI Selected as System Clock source */
uint32_t SystemCoreClock = HSI_VALUE; /*!< System Clock Frequency (Core Clock) */
#endif
//SYS_DIV参数位置，（myInclude.h）
#define SYS_PERIOD 10 /* us */
#define SYS_DIV (uint32_t)(1000000 / SYS_PERIOD)
