M48T86_MIN
m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
tm->tm_min = m48t86_readb(dev, M48T86_MIN);
tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN));