/* Configures the RTC clock (RTCCLK). Once the RTC clock is selected it can be changed unless the Backup domain is reset.  */
void RCC_RTCCLKConfig(RCC_RTCCLKSOURCE_TypeDef rtc_clk_src)
/* Configures the RTC clock (RTCCLK). Once the RTC clock is selected it can be changed unless the Backup domain is reset.  */
void RCC_RTCCLKConfig(RCC_RTCCLKSOURCE_TypeDef rtc_clk_src)
{
    MODIFY_REG(RCC->BDCR, RCC_BDCR_RTCSEL, rtc_clk_src);
}