STM32 F4系列时钟树探索

一、时钟源的基本概念

1.STM32 有5个时钟源:HSI、HSE、LSI、LSE、PLL。

• HSI（High Speed Internal）是高速内部时钟，RC振荡器，频率为16MHz，精度不高。可以直接作为系统时钟或者用作PLL时钟输入。

• HSE（High Speed External）是高速外部时钟，可接石英/陶瓷谐振器，或者接外部时钟源，频率范围为4MHz~26MHz。

• LSI（Low Speed Internal）是低速内部时钟，RC振荡器，频率为32kHz，提供低功耗时钟。主要供独立看门狗和自动唤醒单元使用。

• LSE（Low Speed External）是低速外部时钟，接频率为32.768kHz的石英晶体。RTC。

• PLL为锁相环倍频输出。

2.系统时钟SYSCLK可来源于三个时钟源：

• HSI振荡器时钟
• HSE振荡器时钟
• PLL时钟

3.任何一个外设在使用之前，必须首先使能其相应的时钟。

二、STM32F4系列时钟树

三、RCC相关配置寄存器

typedef struct
{
  __IO uint32_t CR;          
  __IO uint32_t PLLCFGR;       
  __IO uint32_t CFGR;          /*!< RCC clock configuration register,                            Address offset: 0x08 */
  __IO uint32_t CIR;           /*!< RCC clock interrupt register,                                Address offset: 0x0C */
  __IO uint32_t AHB1RSTR;      /*!< RCC AHB1 peripheral reset register,                          Address offset: 0x10 */
  __IO uint32_t AHB2RSTR;      /*!< RCC AHB2 peripheral reset register,                          Address offset: 0x14 */
  __IO uint32_t AHB3RSTR;      /*!< RCC AHB3 peripheral reset register,                          Address offset: 0x18 */
  uint32_t      RESERVED0;     /*!< Reserved, 0x1C                                                                    */
  __IO uint32_t APB1RSTR;      /*!< RCC APB1 peripheral reset register,                          Address offset: 0x20 */
  __IO uint32_t APB2RSTR;      /*!< RCC APB2 peripheral reset register,                          Address offset: 0x24 */
  uint32_t      RESERVED1[2];  /*!< Reserved, 0x28-0x2C                                                               */
  __IO uint32_t AHB1ENR;       /*!< RCC AHB1 peripheral clock register,                          Address offset: 0x30 */
  __IO uint32_t AHB2ENR;       /*!< RCC AHB2 peripheral clock register,                          Address offset: 0x34 */
  __IO uint32_t AHB3ENR;       /*!< RCC AHB3 peripheral clock register,                          Address offset: 0x38 */
  uint32_t      RESERVED2;     /*!< Reserved, 0x3C                                                                    */
  __IO uint32_t APB1ENR;       /*!< RCC APB1 peripheral clock enable register,                   Address offset: 0x40 */
  __IO uint32_t APB2ENR;       /*!< RCC APB2 peripheral clock enable register,                   Address offset: 0x44 */
  uint32_t      RESERVED3[2];  /*!< Reserved, 0x48-0x4C                                                               */
  __IO uint32_t AHB1LPENR;     /*!< RCC AHB1 peripheral clock enable in low power mode register, Address offset: 0x50 */
  __IO uint32_t AHB2LPENR;     /*!< RCC AHB2 peripheral clock enable in low power mode register, Address offset: 0x54 */
  __IO uint32_t AHB3LPENR;     /*!< RCC AHB3 peripheral clock enable in low power mode register, Address offset: 0x58 */
  uint32_t      RESERVED4;     /*!< Reserved, 0x5C                                                                    */
  __IO uint32_t APB1LPENR;     /*!< RCC APB1 peripheral clock enable in low power mode register, Address offset: 0x60 */
  __IO uint32_t APB2LPENR;     /*!< RCC APB2 peripheral clock enable in low power mode register, Address offset: 0x64 */
  uint32_t      RESERVED5[2]; 
  __IO uint32_t BDCR;        
  __IO uint32_t CSR;          
  uint32_t      RESERVED6[2]; 
  __IO uint32_t SSCGR;         
  __IO uint32_t PLLI2SCFGR;   
  __IO uint32_t PLLSAICFGR;    
  __IO uint32_t DCKCFGR;       
} RCC_TypeDef;

四、RCC相关头文件和固件库源文件

1.时钟使能配置:
    RCC_HSICmd, RCC_LSICmd, RCC_PLLCmd, RCC_PLLI2SCmd, RCC_PLLSAICmd, RCC_RTCCLKCmd，RCC_AHBxPeriphClockCmd
    RCC_APBxPeriphClockCmd

2.时钟源和时钟相关配置：
    RCC_HSEConfig, RCC_LSEConfig, RCC_PLLConfig, RCC_PLLI2SConfig, RCC_PLLSAIConfig, RCC_MCO1Config, RCC_MCO2Config, RCC_SYSCLKConfig, RCC_HCLKConfig，RCC_PCLK1Config，RCC_PCLK2Config，RCC_RTCCLKConfig，RCC_I2SCLKConfig

3.外设复位函数
    RCC_AHB1PeriphResetCmd，RCC_AHB2PeriphResetCmd，RCC_AHB3PeriphResetCmd，RCC_APB1PeriphResetCmd，RCC_APB2PeriphResetCmd

4.状态参数获取参数：
    RCC_GetSYSCLKSource，RCC_GetClocksFreq，RCC_GetFlagStatus，RCC_ClearFlag

5.RCC中断相关函数 :
    RCC_ITConfig，RCC_ClearITPendingBit，RCC_GetITStatus