RTC_CTRL_A
ctrla = rtc->read(rtc, RTC_CTRL_A);
rtc->write(rtc, RTC_CTRL_A, ctrla);
ctrla = rtc->read(rtc, RTC_CTRL_A);
rtc->write(rtc, RTC_CTRL_A, ctrla);
rtc->write(rtc, RTC_CTRL_A,
(rtc->read(rtc, RTC_CTRL_A) & ~(RTC_CTRL_A_DV0)));
rtc->write(rtc, RTC_CTRL_A,
(rtc->read(rtc, RTC_CTRL_A) | RTC_CTRL_A_DV0));
ctrla = rtc->read(rtc, RTC_CTRL_A);