ADC_ADCCON
bus_space_write_4(sc->iot, sc->ioh, ADC_ADCCON, 0);
reg = bus_space_read_4(sc->iot, sc->ioh, ADC_ADCCON);
bus_space_write_4(sc->iot, sc->ioh, ADC_ADCCON,
bus_space_write_4(sc->iot, sc->ioh, ADC_ADCCON, adccon);