/**
* @brief Sets System clock frequency to 64MHz and configure HCLK, PCLK2
* and PCLK1 prescalers.
* @note OCS is HSI. This function should be used only after reset.
* @param None
* @retval None
*/
void SetSysClockTo64Mhz(void)
{
__IO uint32_t StartUpCounter = 0, HSEStatus = 0;
RCC_DeInit();
/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/
/* Enable HSI */
RCC->CR |= ((uint32_t)RCC_CR_HSION);
/* Wait till HSI is ready and if Time out is reached exit */
do
{
HSEStatus = RCC->CR & RCC_CR_HSIRDY;
StartUpCounter++;
} while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));
if ((RCC->CR & RCC_CR_HSIRDY) != RESET)
{
HSEStatus = (uint32_t)0x01;
}
else
{
HSEStatus = (uint32_t)0x00;
}
if (HSEStatus == (uint32_t)0x01)
{
/* Enable Prefetch Buffer */
FLASH->ACR |= FLASH_ACR_PRFTBE;
/* Flash 2 wait state */
FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);
FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_2;
/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
/* PCLK2 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;
/* PCLK1 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV2;
/* PLL configuration: PLLCLK = HSI/2 * 16 = 64 MHz */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE |
RCC_CFGR_PLLMULL));
RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSI_Div2| RCC_CFGR_PLLMULL16);
/* 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)0x08)
{
}
}
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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推荐阅读最新更新时间:2024-03-16 16:07