DS1511_CONTROL_B
rtc_write(rtc_read(DS1511_CONTROL_B) | (enabled ? DS1511_TIE : 0), DS1511_CONTROL_B);
alrm->enabled = !!(rtc_read(DS1511_CONTROL_B) & DS1511_TIE);
rtc_write(DS1511_BME, DS1511_CONTROL_B);
rtc_write((rtc_read(DS1511_CONTROL_B) & ~DS1511_TE), DS1511_CONTROL_B);
rtc_write((rtc_read(DS1511_CONTROL_B) | DS1511_TE), DS1511_CONTROL_B);