ST STM32L0x3 User Manual

Code examples RM0367
982/1043 RM0367 Rev 7
A.4 Clock Controller
A.4.1 HSE start sequence code example
/**
* This function enables the interrupton HSE ready,
* and start the HSE as external clock.
* Param None
* Retval None
*/
__INLINE void StartHSE(void)
{
/* Configure NVIC for RCC */
/* (1) Enable Interrupt on RCC */
/* (2) Set priority for RCC */
NVIC_EnableIRQ(RCC_CRS_IRQn); /* (1) */
NVIC_SetPriority(RCC_CRS_IRQn,0); /* (2) */
/* (1) Enable interrupt on HSE ready */
/* (2) Enable the CSS
Enable the HSE and set HSEBYP to use the external clock
instead of an oscillator
Enable HSE */
/* Note : the clock is switched to HSE in the RCC_CRS_IRQHandler ISR */
RCC->CIER |= RCC_CIER_HSERDYIE; /* (1) */
RCC->CR |= RCC_CR_CSSHSEON | RCC_CR_HSEBYP | RCC_CR_HSEON; /* (2) */
}
/**
* This function handles RCC interrupt request
* and switch the system clock to HSE.
* Param None
* Retval None
*/
void RCC_CRS_IRQHandler(void)
{
/* (1) Check the flag HSE ready */
/* (2) Clear the flag HSE ready */
/* (3) Switch the system clock to HSE */
if ((RCC->CifR & RCC_CifR_HSERDYF) != 0) /* (1) */
{
RCC->CICR |= RCC_CICR_HSERDYC
; /* (2) */
RCC->CFGR = ((RCC->CFGR & (~RCC_CFGR_SW)) | RCC_CFGR_SW_HSE); /* (3) */
}
else

ST STM32L0x3 Specifications

General

Brand	ST
Model	STM32L0x3
Category	Microcontrollers
Language	English