STM32F4库函数里面的RCC_DeInit(void)函数分析

void RCC_DeInit(void)

{

/*Set HSION bit，内部高速时钟使能HSI振荡器打开*/

RCC->CR |=(uint32_t)0x00000001;

/*Reset CFGR register,

31:30--00：选择系统时钟 (SYSCLK) 输出到 MCO2 引脚

27:29--0xx:MCO2 预分频器 (MCO2 prescaler)无分频

24:26--0xx:MCO1 预分频器 (MCO1 prescaler)无分频

23--0：PLLI2S 时钟用作 I2S 时钟源

22:21--00：选择 HSI 时钟输出到 MCO1 引脚

20:16--00000：无时钟，适用于 RTC 时钟的 HSE 分频系数

15:13--0xx：AHB 时钟不分频

12:10--0xx：AHB 时钟不分频

9:8 保留，必须保持复位值

7:4--AHB 预分频器 (AHB prescaler)，0xxx：系统时钟不分频

3:2 --SWS：系统时钟切换状态 (System clock switch status)，00：HSI 振荡器用作系统时钟

1:0-- SW：系统时钟切换 (System clock switch)，00：选择 HSI 振荡器作为系统时钟*/

RCC->CFGR = 0x00000000;

/* Reset HSEON, CSSON, PLLON, PLLI2S and PLLSAI(STM32F42xxx/43xxx/446xx/469xx/479xx devices) bits

HSEON：0：HSE 振荡器关闭，HSE 时钟使能 (HSE clock enable)

CSSON：时钟安全系统使能 (Clock security system enable)，0：时钟安全系统关闭（时钟监测器关闭）

PLLON：主 PLL (PLL) 使能 (Main PLL (PLL) enable)，0：PLL 关闭

PLLI2S：PLLI2S 使能 (PLLI2S enable)，0：PLLI2S 关闭

PLLSAI：无*/
 RCC->CR &= (uint32_t)0xEAF6FFFF;

/* Reset PLLCFGR register */   RCC->PLLCFGR = 0x24003010;

#if defined(STM32F40_41xxx) || defined(STM32F427_437xx) || defined(STM32F429_439xx) || defined(STM32F401xx) || defined(STM32F411xE) || defined(STM32F446xx) || defined(STM32F469_479xx)    /* Reset PLLI2SCFGR register */

RCC->PLLI2SCFGR = 0x20003000;

#endif /* STM32F40_41xxx || STM32F427_437xx || STM32F429_439xx || STM32F401xx || STM32F411xE || STM32F446xx || STM32F469_479xx */

#if defined(STM32F40_41xxx) || defined(STM32F427_437xx) || defined(STM32F429_439xx) || defined(STM32F446xx) || defined(STM32F469_479xx)   /* Reset PLLSAICFGR register, only available for STM32F42xxx/43xxx/446xx/469xx/479xx devices */

RCC->PLLSAICFGR = 0x24003000;

#endif /* STM32F40_41xxx || STM32F427_437xx || STM32F429_439xx || STM32F446xx || STM32F469_479xx */

/* Reset HSEBYP bit */

RCC->CR &= (uint32_t)0xFFFBFFFF;

/* Disable all interrupts */

RCC->CIR = 0x00000000;

/* Disable Timers clock prescalers selection, only available for STM32F42/43xxx devices */   RCC->DCKCFGR = 0x00000000;

#if defined(STM32F410xx)

/* Disable LPTIM and FMPI2C clock prescalers selection, only available for STM32F410xx devices */

RCC->DCKCFGR2 = 0x00000000;

#endif /* STM32F410xx */  }

}