stm32 systick使用
一开始在stm32参考手册里找关于systick的内容，没找到任何有用的信息，后来百度了下，发现是在cortex m3参考手册里有
几个寄存器的描述在第8.2节，寄存器的定义在core_cm3.h中而不是stm32f10.h，应该这个systick是属于cm3内核的内容，所以才放在这个文件中定义。
先来看看是如何定义的：
/* Memory mapping of Cortex-M3 Hardware */
#define SCS_BASE (0xE000E000) /*!< System Control Space Base Address */
#define ITM_BASE (0xE0000000) /*!< ITM Base Address */
#define CoreDebug_BASE (0xE000EDF0) /*!< Core Debug Base Address */
#define SysTick_BASE (SCS_BASE + 0x0010) /*!< SysTick Base Address */
#define NVIC_BASE (SCS_BASE + 0x0100) /*!< NVIC Base Address */
#define SCB_BASE (SCS_BASE + 0x0D00) /*!< System Control Block Base Address */
#define InterruptType ((InterruptType_Type *) SCS_BASE) /*!< Interrupt Type Register */
#define SCB ((SCB_Type *) SCB_BASE) /*!< SCB configuration struct */
#define SysTick ((SysTick_Type *) SysTick_BASE) /*!< SysTick configuration struct */
#define NVIC ((NVIC_Type *) NVIC_BASE) /*!< NVIC configuration struct */
#define ITM ((ITM_Type *) ITM_BASE) /*!< ITM configuration struct */
#define CoreDebug ((CoreDebug_Type *) CoreDebug_BASE) /*!< Core Debug configuration struct */
#if defined (__MPU_PRESENT) && (__MPU_PRESENT == 1)
#define MPU_BASE (SCS_BASE + 0x0D90) /*!< Memory Protection Unit */
#define MPU ((MPU_Type*) MPU_BASE) /*!< Memory Protection Unit */
#endif
可以看到，中间有systick的定义，类型为结构体指针，该结构体定义如下
typedef struct
{
__IO uint32_t CTRL; /*!< Offset: 0x00 SysTick Control and Status Register */
__IO uint32_t LOAD; /*!< Offset: 0x04 SysTick Reload Value Register */
__IO uint32_t VAL; /*!< Offset: 0x08 SysTick Current Value Register */
__I uint32_t CALIB; /*!< Offset: 0x0C SysTick Calibration Register */
} SysTick_Type;
可以看到，systick相关的四个寄存器都定义了，后面还很方便的把各个为的功能都用宏定义指明了，如下
/* SysTick Control / Status Register Definitions */
#define SysTick_CTRL_COUNTFLAG_Pos 16 /*!< SysTick CTRL: COUNTFLAG Position */
#define SysTick_CTRL_COUNTFLAG_Msk (1ul << SysTick_CTRL_COUNTFLAG_Pos) /*!< SysTick CTRL: COUNTFLAG Mask */
#define SysTick_CTRL_CLKSOURCE_Pos 2 /*!< SysTick CTRL: CLKSOURCE Position */
#define SysTick_CTRL_CLKSOURCE_Msk (1ul << SysTick_CTRL_CLKSOURCE_Pos) /*!< SysTick CTRL: CLKSOURCE Mask */
#define SysTick_CTRL_TICKINT_Pos 1 /*!< SysTick CTRL: TICKINT Position */
#define SysTick_CTRL_TICKINT_Msk (1ul << SysTick_CTRL_TICKINT_Pos) /*!< SysTick CTRL: TICKINT Mask */
#define SysTick_CTRL_ENABLE_Pos 0 /*!< SysTick CTRL: ENABLE Position */
#define SysTick_CTRL_ENABLE_Msk (1ul << SysTick_CTRL_ENABLE_Pos) /*!< SysTick CTRL: ENABLE Mask */
/* SysTick Reload Register Definitions */
#define SysTick_LOAD_RELOAD_Pos 0 /*!< SysTick LOAD: RELOAD Position */
#define SysTick_LOAD_RELOAD_Msk (0xFFFFFFul << SysTick_LOAD_RELOAD_Pos) /*!< SysTick LOAD: RELOAD Mask */
/* SysTick Current Register Definitions */
#define SysTick_VAL_CURRENT_Pos 0 /*!< SysTick VAL: CURRENT Position */
#define SysTick_VAL_CURRENT_Msk (0xFFFFFFul << SysTick_VAL_CURRENT_Pos) /*!< SysTick VAL: CURRENT Mask */
/* SysTick Calibration Register Definitions */
#define SysTick_CALIB_NOREF_Pos 31 /*!< SysTick CALIB: NOREF Position */
#define SysTick_CALIB_NOREF_Msk (1ul << SysTick_CALIB_NOREF_Pos) /*!< SysTick CALIB: NOREF Mask */
#define SysTick_CALIB_SKEW_Pos 30 /*!< SysTick CALIB: SKEW Position */
#define SysTick_CALIB_SKEW_Msk (1ul << SysTick_CALIB_SKEW_Pos) /*!< SysTick CALIB: SKEW Mask */
#define SysTick_CALIB_TENMS_Pos 0 /*!< SysTick CALIB: TENMS Position */
#define SysTick_CALIB_TENMS_Msk (0xFFFFFFul << SysTick_VAL_CURRENT_Pos) /*!< SysTick CALIB: TENMS Mask */
/*@}*/ /* end of group CMSIS_CM3_SysTick */
pos指明偏移位数，1ul的ul表明1为unsigned long型数据，32位
接下来看看各个位的具体描述，先是控制寄存器
重装载寄存器里面就放重装载值
目前值寄存器就是保存目前值，最后一个校准没用到。
以下为秒钟的测试
main部分代码----------------
SysTick->CTRL&=~SysTick_CTRL_CLKSOURCE_Msk;//clksource清零
SysTick->CTRL|=SysTick_CTRL_CLKSOURCE_Msk;//clksource置1
SysTick->CTRL|=SysTick_CTRL_TICKINT_Msk;//开中断
SysTick->LOAD=72000;//设置重装载值 1ms
SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk;//启动systick
while(1)
{
if(cnt==1000)
{
sec++;
cnt=0;
LCD_ShowNum(30,30,sec,10,12);
}
}
中断部分，在stm32f10x_it.c
void SysTick_Handler(void)
{
extern u32 cnt;
cnt++;
}
刚刚发现，在core_cm3.h中已经有个函数用于设置systick，为SysTick_Config