A display device is arranged so as to be able to conduct a touch detection action for sensing a region where a touch operation on a touch panel has been performed, to stop the touch detection action in the touch panel, and to specify a touch-detection-stop region. The display device includes an image-display-direction register. A processor writes parameters designating an image-display direction into the image-display-direction register based on a result of detection by a tilt detector. On condition that parameters stored in the image-display-direction register have been changed, the display device changes the touch-detection-stop region based on the parameters. The above function is mounted on a semiconductor integrated circuit device included in the display device.