2018年10月17日 | STM32时钟RCC详解（四）

RCC实例详解

#if defined (STM32F10X_LD_VL) || (defined STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)//如果定义了这些系统时钟将设为24M，如果没有定义则为72M

 #define SYSCLK_FREQ_24MHz  24000000
#else

 



#define SYSCLK_FREQ_72MHz  72000000      //系统时钟默认值的定义 ，如果没有定义外部高速时钟则用内部高速时钟，为8000000

#endif

 
#if defined (STM32F10X_HD) || (defined STM32F10X_XL) || (defined STM32F10X_HD_VL)//内外部SRAM选择

#endif

 

#define VECT_TAB_OFFSET  0x0

#ifdef SYSCLK_FREQ_HSE
  uint32_t SystemCoreClock         = SYSCLK_FREQ_HSE;       
#elif defined SYSCLK_FREQ_24MHz
  uint32_t SystemCoreClock         = SYSCLK_FREQ_24MHz;       
#elif defined SYSCLK_FREQ_36MHz
  uint32_t SystemCoreClock         = SYSCLK_FREQ_36MHz;       
#elif defined SYSCLK_FREQ_48MHz
  uint32_t SystemCoreClock         = SYSCLK_FREQ_48MHz;       
#elif defined SYSCLK_FREQ_56MHz
  uint32_t SystemCoreClock         = SYSCLK_FREQ_56MHz;       
#elif defined SYSCLK_FREQ_72MHz
  uint32_t SystemCoreClock         = SYSCLK_FREQ_72MHz;       
#else 
  uint32_t SystemCoreClock         = HSI_VALUE;       
#endif

__I uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};//AHB配方表

static void SetSysClock(void); //设置系统时钟的函数声明
//以下为根据不同的系统时钟的定义来声明用到的相应的函数，为后面的函数调用做好准备
#ifdef SYSCLK_FREQ_HSE
  static void SetSysClockToHSE(void);
#elif defined SYSCLK_FREQ_24MHz
  static void SetSysClockTo24(void);
#elif defined SYSCLK_FREQ_36MHz
  static void SetSysClockTo36(void);
#elif defined SYSCLK_FREQ_48MHz
  static void SetSysClockTo48(void);
#elif defined SYSCLK_FREQ_56MHz
  static void SetSysClockTo56(void);  
#elif defined SYSCLK_FREQ_72MHz
  static void SetSysClockTo72(void);
#endif

#ifdef DATA_IN_ExtSRAM //外部SRAM选择后的初始化函数声明
  static void SystemInit_ExtMemCtl(void); 
#endif

void SystemInit (void)//系统初始化函数，设置系统的时钟及时钟中断（在startup_stm32f10x_md.s中调用）(复位RCC时钟配置为默认状态，直到设置时钟函数)
{
 
 
  RCC->CR |= (uint32_t)0x00000001; //内部高速时钟使能,内部8MHz时钟开启

 
#ifndef STM32F10X_CL
  RCC->CFGR &= (uint32_t)0xF8FF0000;//MCO微控制器没有时钟输出(对外部引脚),ADC预分频PCLK2 2分频后作为ADC时钟,APB预分频HCLK不分频,AHB预分频SYSCLK不分频,HSI作为系统时钟
                                    //HSI作为系统时钟输出（已输出），SYSCLK=PCLK=PCLK1=PCLK2=8M，ADCCLK=1/2(PCLK2)=4M
#else
  RCC->CFGR &= (uint32_t)0xF0FF0000;//同上；RCC->CFGR的27位为保留位始终为0 ，HSI作为系统时钟输出（未输出原因为未编译）
#endif    
  
 
  RCC->CR &= (uint32_t)0xFEF6FFFF;//时钟监测器关闭,HSE振荡器关闭

 
  RCC->CR &= (uint32_t)0xFFFBFFFF;//外部4-25MHz振荡器没有旁路

 
  RCC->CFGR &= (uint32_t)0xFF80FFFF; //PLL时钟1.5倍分频作为USB时钟,PLL 2倍频输出,HSE不分频,HSI时钟2分频后作为PLL输入时钟
                                     //PLLCLK=HSICLK=8M（还未输出）,HSECLK=HSEOSC,USBCLK=PLLCLK/1.5 ，除PLL外其他分频系数都为0
#ifdef STM32F10X_CL
 
  RCC->CR &= (uint32_t)0xEBFFFFFF;//CR中的26和28位置0

 
  RCC->CIR = 0x00FF0000;//清除中断标志，关闭一些中断

 
  RCC->CFGR2 = 0x00000000; //没有此寄存器
#elif defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)
 
  RCC->CIR = 0x009F0000;//清除中断标志，关闭一些中断

 
  RCC->CFGR2 = 0x00000000; //没有此寄存器     
#else
 
  RCC->CIR = 0x009F0000; //清除中断标志，关闭一些中断
#endif
    
#if defined (STM32F10X_HD) || (defined STM32F10X_XL) || (defined STM32F10X_HD_VL)
  #ifdef DATA_IN_ExtSRAM
    SystemInit_ExtMemCtl();//如果宏定义了外部SRAM则对其初始化控制
  #endif
#endif

 
 
  SetSysClock();//设置系统时钟

#ifdef VECT_TAB_SRAM
  SCB->VTOR = SRAM_BASE | VECT_TAB_OFFSET;
#else
  SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET;
#endif 
}

void SystemCoreClockUpdate (void)
{
  uint32_t tmp = 0, pllmull = 0, pllsource = 0;

#ifdef  STM32F10X_CL
  uint32_t prediv1source = 0, prediv1factor = 0, prediv2factor = 0, pll2mull = 0;
#endif

#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)
  uint32_t prediv1factor = 0;
#endif
    
 
  tmp = RCC->CFGR & RCC_CFGR_SWS;
  
  switch (tmp)
  {
    case 0x00: 
      SystemCoreClock = HSI_VALUE;
      break;
    case 0x04: 
      SystemCoreClock = HSE_VALUE;
      break;
    case 0x08: 

     
      pllmull = RCC->CFGR & RCC_CFGR_PLLMULL;
      pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;
      
#ifndef STM32F10X_CL      
      pllmull = ( pllmull >> 18) + 2;
      
      if (pllsource == 0x00)
      {
       
        SystemCoreClock = (HSI_VALUE >> 1) * pllmull;
      }
      else
      {
 #if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)
       prediv1factor = (RCC->CFGR2 & RCC_CFGR2_PREDIV1) + 1;
      
       SystemCoreClock = (HSE_VALUE / prediv1factor) * pllmull; 
 #else
       
        if ((RCC->CFGR & RCC_CFGR_PLLXTPRE) != (uint32_t)RESET)
        {
          SystemCoreClock = (HSE_VALUE >> 1) * pllmull;
        }
        else
        {
          SystemCoreClock = HSE_VALUE * pllmull;
        }
 #endif
      }
#else
      pllmull = pllmull >> 18;
      
      if (pllmull != 0x0D)
      {
         pllmull += 2;
      }
      else
      {
        pllmull = 13 / 2; 
      }
            
      if (pllsource == 0x00)
      {
       
        SystemCoreClock = (HSI_VALUE >> 1) * pllmull;
      }
      else
      {
        
       
        prediv1source = RCC->CFGR2 & RCC_CFGR2_PREDIV1SRC;
        prediv1factor = (RCC->CFGR2 & RCC_CFGR2_PREDIV1) + 1;
        
        if (prediv1source == 0)
        { 
         
          SystemCoreClock = (HSE_VALUE / prediv1factor) * pllmull;          
        }
        else
        {
          
         
          prediv2factor = ((RCC->CFGR2 & RCC_CFGR2_PREDIV2) >> 4) + 1;
          pll2mull = ((RCC->CFGR2 & RCC_CFGR2_PLL2MUL) >> 8 ) + 2; 
          SystemCoreClock = (((HSE_VALUE / prediv2factor) * pll2mull) / prediv1factor) * pllmull;                         
        }
      }
#endif  
      break;

    default:
      SystemCoreClock = HSI_VALUE;
      break;
  }
  
 
 
  tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];
 
  SystemCoreClock >>= tmp;  
}

static void SetSysClock(void)//根据不同的宏定义，设置不同的系统时钟
{  
#ifdef SYSCLK_FREQ_HSE
  SetSysClockToHSE();
#elif defined SYSCLK_FREQ_24MHz
  SetSysClockTo24();
#elif defined SYSCLK_FREQ_36MHz
  SetSysClockTo36();
#elif defined SYSCLK_FREQ_48MHz
  SetSysClockTo48();
#elif defined SYSCLK_FREQ_56MHz
  SetSysClockTo56();  
#elif defined SYSCLK_FREQ_72MHz
  SetSysClockTo72(); 
#endif
 
  
}

 
#ifdef DATA_IN_ExtSRAM
 
void SystemInit_ExtMemCtl(void) 
{

 
  RCC->AHBENR = 0x00000114;
  
    
  RCC->APB2ENR = 0x000001E0;
  


  


  
  GPIOD->CRL = 0x44BB44BB;  
  GPIOD->CRH = 0xBBBBBBBB;

  GPIOE->CRL = 0xB44444BB;  
  GPIOE->CRH = 0xBBBBBBBB;

  GPIOF->CRL = 0x44BBBBBB;  
  GPIOF->CRH = 0xBBBB4444;

  GPIOG->CRL = 0x44BBBBBB;  
  GPIOG->CRH = 0x44444B44;
   
  

  
  FSMC_Bank1->BTCR[4] = 0x00001011;
  FSMC_Bank1->BTCR[5] = 0x00000200;
}
#endif

#ifdef SYSCLK_FREQ_HSE

static void SetSysClockToHSE(void)
{
  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;
  
      
      
  RCC->CR |= ((uint32_t)RCC_CR_HSEON);
 
 
  do
  {
    HSEStatus = RCC->CR & RCC_CR_HSERDY;
    StartUpCounter++;  
  } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

  if ((RCC->CR & RCC_CR_HSERDY) != RESET)
  {
    HSEStatus = (uint32_t)0x01;
  }
  else
  {
    HSEStatus = (uint32_t)0x00;
  } 

  if (HSEStatus == (uint32_t)0x01)
  {

#if !defined STM32F10X_LD_VL && !defined STM32F10X_MD_VL && !defined STM32F10X_HD_VL
   
    FLASH->ACR |= FLASH_ACR_PRFTBE;

   
    FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);

#ifndef STM32F10X_CL
    FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_0;
#else
    if (HSE_VALUE <= 24000000)
 {
      FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_0;
 }
 else
 {
      FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_1;
 }
#endif
#endif
 
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
      
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;
    
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV1;
    
   
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
    RCC->CFGR |= (uint32_t)RCC_CFGR_SW_HSE;   

   
    while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)0x04)
    {
    }
  }
  else
  {
  }  
}
#elif defined SYSCLK_FREQ_24MHz

static void SetSysClockTo72(void)//系统时钟设置为72M：SYSCLK=72M，HCLK=72M，PCLK1=36M（最高36M），PCLK2=72M，ADCCLK=36M,
{
  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;//启动计数，HSE状态
  
      
      
  RCC->CR |= ((uint32_t)RCC_CR_HSEON);//HSE使能
 
 
  do //循环，直到HSE使能成功或者超时
  {
    HSEStatus = RCC->CR & RCC_CR_HSERDY;
    StartUpCounter++;  
  } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

  if ((RCC->CR & RCC_CR_HSERDY) != RESET)
  {
    HSEStatus = (uint32_t)0x01;//HSE使能成功
  }
  else
  {
    HSEStatus = (uint32_t)0x00;//HSE使能不成功
  } 

  if (HSEStatus == (uint32_t)0x01)//HSE使能成功
  {
   
    FLASH->ACR |= FLASH_ACR_PRFTBE;//flash缓存使能

   
    FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);//
    FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_2;//   

 
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;//RCC_CFGR_HPRE_DIV1=0，CFGR中的值不变
      
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;//RCC_CFGR_PPRE2_DIV1=0，CFGR中的值不变
    
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV2;//低速APB预分频把HCLK 2分频,APB1CLK=HCLK/2

#ifdef STM32F10X_CL
   
   
   
        
    RCC->CFGR2 &= (uint32_t)~(RCC_CFGR2_PREDIV2 | RCC_CFGR2_PLL2MUL |
                              RCC_CFGR2_PREDIV1 | RCC_CFGR2_PREDIV1SRC);
    RCC->CFGR2 |= (uint32_t)(RCC_CFGR2_PREDIV2_DIV5 | RCC_CFGR2_PLL2MUL8 |
                             RCC_CFGR2_PREDIV1SRC_PLL2 | RCC_CFGR2_PREDIV1_DIV5);
  
   
    RCC->CR |= RCC_CR_PLL2ON;
   
    while((RCC->CR & RCC_CR_PLL2RDY) == 0)
    {
    }
    
   
     
    RCC->CFGR &= (uint32_t)~(RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLSRC | RCC_CFGR_PLLMULL);
    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLXTPRE_PREDIV1 | RCC_CFGR_PLLSRC_PREDIV1 | 
                            RCC_CFGR_PLLMULL9); 
#else    
   
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE |  //PLL输入时钟源HSI时钟2分频后作为PLL输入时钟,HSE分频器作为PLL输入HSE不分频 
                                        RCC_CFGR_PLLMULL)); //PLL倍频系数PLL 2倍频输出（为了清零其他位）
    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSE | RCC_CFGR_PLLMULL9);//PLL输入时钟源HSE时钟作为PLL输入时钟,PLL倍频系数PLL 9倍频输出 
#endif

   
    RCC->CR |= RCC_CR_PLLON; //PLL使能

   
    while((RCC->CR & RCC_CR_PLLRDY) == 0)//等待PLL使能成功
    {
    }
    
   
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));//HSI作为系统时钟(为了清零其他位)
    RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL; //PLL输出作为系统时钟  

   
    while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)0x08)//等待直到PLL成功用作系统时钟源
    {
    }
  }
  else
  {
  }
}
#endif