In conventional liquid crystal display controllers, the display is reduced in the stand-by state but the liquid crystal display duty is not changed, i.e., even the common electrodes of the rows that are not producing display are scanned, and the consumption of electric power is not decreased to a sufficient degree in the stand-by state. A liquid crystal display controller includes a drive duty selection register capable of being rewritten by a microprocessor, and a drive bias selection register. When the display is changed from the whole display on a liquid crystal display panel to a partial display on part of the rows only, the preset values of the drive duty selection register and of the drive bias selection register are changed, so that the display is selectively produced on a portion of the liquid crystal display panel at a low voltage with a low-duty drive.