RTC_CENTURY
century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
century = rtc->read(rtc, RTC_CENTURY);
rtc->write(rtc, RTC_CENTURY, century);
cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
century = readb(ioaddr + RTC_CENTURY);
writeb(bin2bcd((tm->tm_year + 1900) / 100), ioaddr + RTC_CENTURY);