RTC_YEAR
ds1687_write(sc, RTC_YEAR, dt->dt_year % 100);
dt->dt_year = ds1687_read(sc, RTC_YEAR);
dt->dt_year = RTC_REG(RTC_YEAR10) * 10 + RTC_REG(RTC_YEAR)
RTC_WRITE(RTC_YEAR, year2);