RHRCNT
unsigned char buf[] = { RSECCNT, RMINCNT, RHRCNT,
ret = write_reg(dev, RHRCNT, bin2bcd(dt->tm_hour));
tm->tm_hour = bcd2bin(readb(rtc->regbase + RHRCNT));
writeb(bin2bcd(tm->tm_hour), rtc->regbase + RHRCNT);