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__HAL_RCC_LSE_CONFIG macro
Macro to configure the External Low Speed oscillator (LSE).
Syntax
#define __HAL_RCC_LSE_CONFIG(__STATE__) \
do { \
if((__STATE__) == RCC_LSE_ON) \
{ \
SET_BIT(RCC->BDCR, RCC_BDCR_LSEON); \
} \
else if((__STATE__) == RCC_LSE_BYPASS) \
{ \
SET_BIT(RCC->BDCR, RCC_BDCR_LSEBYP); \
SET_BIT(RCC->BDCR, RCC_BDCR_LSEON); \
} \
else \
{ \
CLEAR_BIT(RCC->BDCR, RCC_BDCR_LSEON); \
CLEAR_BIT(RCC->BDCR, RCC_BDCR_LSEBYP); \
} \
} while(0U)
Notes
Transition LSE Bypass to LSE On and LSE On to LSE Bypass are not supported by this macro. User should request a transition to LSE Off first and then LSE On or LSE Bypass. As the LSE is in the Backup domain and write access is denied to this domain after reset, you have to enable write access using HAL_PWR_EnableBkUpAccess() function before to configure the LSE (to be done once after reset). After enabling the LSE (RCC_LSE_ON or RCC_LSE_BYPASS), the application software should wait on LSERDY flag to be set indicating that LSE clock is stable and can be used to clock the RTC.