ADC_WRITE_PNTR_REG
status = readw(devpriv->main_iobase + ADC_WRITE_PNTR_REG);
write_index = readw(devpriv->main_iobase + ADC_WRITE_PNTR_REG) &
readw(devpriv->main_iobase + ADC_WRITE_PNTR_REG) & 0x7fff;