一開始在stm32參考手冊裏找關於systick的內容，沒找到任何有用的信息，後來百度了下，發現是在cortex m3參考手冊裏有

幾個寄存器的描述在第8.2節，寄存器的定義在core_cm3.h中而不是stm32f10.h，應該這個systick是屬於cm3內核的內容，所以才放在這個文件中定義。

先來看看是如何定義的：

/* 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，中間有systick的定義，類型為結構體指針，該結構體定義如下

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相關的四個寄存器都定義了，後面還很方便的把各個為的功能都用宏定義指明了，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指明偏移位數，1ul的ul表明1為unsigned long型數據，32位

接下來看看各個位的具體描述，先是控制寄存器

重裝載寄存器裏面就放重裝載值

目前值寄存器就是保存目前值，最後一個校準沒用到。

以下為秒鐘的測試

main部分代碼----------------

    SysTick->CTRL&=~SysTick_CTRL_CLKSOURCE_Msk;//clksource清零
    SysTick->CTRL|=SysTick_CTRL_CLKSOURCE_Msk;//clksource置1
    
    SysTick->CTRL|=SysTick_CTRL_TICKINT_Msk;//開中斷
    
    SysTick->LOAD=72000;//設置重裝載值 1ms
    SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk;//啟動systick
      while(1) 
    {         
        if(cnt==1000)
        {
            sec++;
            cnt=0;             
            LCD_ShowNum(30,30,sec,10,12);
        }
    } 

中斷部分，在stm32f10x_it.c

void SysTick_Handler(void)
{
    extern u32 cnt;
    cnt++;
}

stm32 systick使用