ADC_SAMPLE_INTERVAL_UPPER_REG
writew(0xff, devpriv->main_iobase + ADC_SAMPLE_INTERVAL_UPPER_REG);
writew(0, devpriv->main_iobase + ADC_SAMPLE_INTERVAL_UPPER_REG);
devpriv->main_iobase + ADC_SAMPLE_INTERVAL_UPPER_REG);