STM32F030F4P6系统时钟必须和AHB时钟一致吗

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yanggong 提问时间：2015-11-21 15:59 /

STM32F030F4P6 外部晶振8M 设置AHB为系统时钟的2-512分频，程序在执行完初始化后就不在执行了，这是为什么？不分频就可以执行

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8个回答

废鱼回答时间：2015-11-21 16:11:43

时钟配置错误。

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yanggong 回答时间：2015-11-21 16:15:05

if (HSEStatus == (uint32_t)0x01)
{
/* Enable Prefetch Buffer and set Flash Latency */
FLASH->ACR = FLASH_ACR_PRFTBE | FLASH_ACR_LATENCY;

/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV2;//这里改成2分频就不行了

/* PCLK = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE_DIV1;

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chifen 回答时间：2015-11-21 16:31:32

不能只看这里一点，要看你的是不是启用了外部时钟，你倍频是多少，才能知道下面的分频

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yanggong 回答时间：2015-11-21 16:33:44

static void SetSysClock(void)
{
  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;

/******************************************************************************/
/*          PLL (clocked by HSE) used as System clock source             */
/******************************************************************************/

  /* SYSCLK, HCLK, PCLK configuration ----------------------------------------*/
  /* Enable HSE */
  RCC->CR |= ((uint32_t)RCC_CR_HSEON);

  /* Wait till HSE is ready and if Time out is reached exit */
  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)
  {
/* Enable Prefetch Buffer and set Flash Latency */
FLASH->ACR = FLASH_ACR_PRFTBE | FLASH_ACR_LATENCY;

/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV2;

/* PCLK = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE_DIV1;

/* PLL configuration */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMULL));
RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_PREDIV1 | RCC_CFGR_PLLXTPRE_PREDIV1 | RCC_CFGR_PLLMULL2);
RCC_PREDIV1Config( RCC_PREDIV1_Div2);
/* Enable PLL */
RCC->CR |= RCC_CR_PLLON;

/* Wait till PLL is ready */
while((RCC->CR & RCC_CR_PLLRDY) == 0)
{
}

/* Select PLL as system clock source */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;

/* Wait till PLL is used as system clock source */
while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)RCC_CFGR_SWS_PLL)
{
}
  }
  else
  { /* If HSE fails to start-up, the application will have wrong clock
      configuration. User can add here some code to deal with this error */
  }
}

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chifen 回答时间：2015-11-21 16:50:29

system_stm32f0xx.c 里看一下
#define PLL_SOURCE_HSI // HSI (~8MHz) used to clock the PLL, and the PLL is used as system clock source
//#define PLL_SOURCE_HSE // HSE (8MHz) used to clock the PLL, and the PLL is used as system clock source
//#define PLL_SOURCE_HSE_BYPASS // HSE bypassed with an external clock (8MHz, coming from ST-Link) used to clock
你启用的是哪个

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