GD32F150x之System Tick

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ARM-M3 时钟控制与System Tick操作。

// created by perry.peng 2013/04/28

void System_Init (void){  RCC->GCCR = RCC_GCCR_HSIEN;                 // 启用内部8MHz RC oscillator。  while (!(RCC->GCCR & RCC_GCCR_HSISTB));     // 等待直到内部RC oscillator稳定。  /* [31]      rw PLLDV    = 0,   CK_OUT的输入分频系数CK_PLL divide by 2.     [30:28]   rw CKOUTDIV = 0,   CK_OUT的输出分频系数。     [26:24]   rw CKOUTSRC = 0,   CKOUT时钟输出PIN的输出频率(No clock selected).     [23:22]   rw USBPS    = 0,   USB时钟等于CK_PLL / 1.5     [27,21:18]rw PLLMF   = 0x12, PLL倍频系数是18x.     [17]      rw PLLPREDV = 0,   PLL时钟源选用HSE时钟(PLLSEL=1时有效).     [16]      rw PLLSEL   = 0,   PLL时钟源等于HSI时钟除2(8MHz / 2)     [15:14]   rw ADCPS    = 0,   ADC时钟等于CK_APB2 / 2.     [13:11]   rw APB2PS   = 0,   APB2时钟等于CK_AHB.     [10:8]    rw APB1PS   = 0,   APB1时钟等于CK_AHB.     [7:4]     rw AHBPS    = 0,   AHB时钟等于CK_SYS.     [3:2]     r  SCSS            System clock switch status(Read only).     [1:0]     rw SCS      = 0,   CK_SYS时钟来自CK_HSI   */  RCC->GCFGR = 0x808000C;  /* [31:26]      Reserved.     [25]      r  PLLSTB          PLL Clock Stabilization Flag, 0: PLL is not stable     [24]      rw PLLEN    = 1,   PLL enable.     [23:20]      Reserved.     [19]      rw CKMEN    = 0,   Disable the External 4 ~ 32 MHz crystal oscillator (HSE) clock monitor.     [18]      rw HSEBPS   = 0,   Disable the HSE Bypass mode.     [17]      r  HSESTB          0: HSE oscillator is not stable     [16]      rw HSEEN    = 0,   0: External 4 ~ 32 MHz crystal oscillator disabled.     [15:8]    r  HSICALIB        High Speed Internal Oscillator calibration value register     [7:3]     rw HSIADJ          High Speed Internal Oscillator clock trim adjust value     [2]          Reserved.     [1]       r  HSISTB          0: HSI oscillator is not stable     [0]       rw HSIEN           1: Internal 8 MHz RC oscillator enabled   */  RCC->GCCR |= RCC_GCCR_PLLEN;  while(!(RCC->GCCR & RCC_GCCR_PLLSTB));      // Wait untill PLL is ready  RCC->GCFGR |= (uint32_t)RCC_GCFGR_SCS_PLL;  // 切换CK_SYS时钟为CK_PLL  /* Wait untill PLL is chosen as system clock source */  while ((RCC->GCFGR & (uint32_t)RCC_GCFGR_SCSS) != (uint32_t)RCC_GCFGR_SCSS_PLL);}/**  * @brief  This function handles SysTick Handler.  * @param  None  * @retval None  */void SysTick_Handler(void){  if (!(++flag % 1000)) {    if (GPIO_ReadOutputBit(GPIOB, GPIO_PIN_10))      GPIO_ResetBits(GPIOB, GPIO_PIN_10);    else      GPIO_SetBits(GPIOB, GPIO_PIN_10);    flag = 0;  }}void delay_us(uint32_t nTime){  SysTick->VAL=0X00;                              //  初值  SysTick->LOAD=72*nTime;                   //  重装值；48个时钟周期=1us  SysTick->CTRL=0x00000005;               //  第0位：使能时钟   第3位：使用内部时钟  while(!(SysTick->CTRL&0x00010000));  //计时  SysTick->CTRL|=0x00000004;             // 第1位：产生异常请求}int main(void){  GPIO_InitPara GPIO_InitStructure;    RCC_AHBPeriphClock_Enable(RCC_AHBPERIPH_GPIOB, ENABLE);  GPIO_InitStructure.GPIO_Pin = GPIO_PIN_10;  GPIO_InitStructure.GPIO_Speed = GPIO_SPEED_50MHZ;  GPIO_InitStructure.GPIO_Mode = GPIO_MODE_OUT;  GPIO_InitStructure.GPIO_OType = GPIO_OTYPE_PP;  GPIO_InitStructure.GPIO_PuPd = GPIO_PUPD_NOPULL;  GPIO_Init(GPIOB, &GPIO_InitStructure);  SysTick_Config(72000);    /// 72000 / 72000000(72MHz) = 0.001秒。    while(1) {    //GPIO_SetBits(GPIOB, GPIO_PIN_11);    //delay_us(1000000);    //GPIO_ResetBits(GPIOB, GPIO_PIN_11);    //delay_us(1000000);  }  return 0;}

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