For each unit transmission block having a pixel data block including at least one pixel data piece, clock data is added contiguously to a head of the pixel data block. If no data transition has occurred at a boundary between the clock data and the pixel data block, logic inversion is performed on the pixel data piece. Thereafter, a transmission image data signal in which unit transmission blocks, each constituted by adding an inversion flag immediately before the clock data, are consecutively arranged is transmitted to a display panel driver. The driver generates a clock signal on the basis of the clock data included in the received signal and takes in the pixel data piece or the resultant obtained by inverting the logic level of this pixel data piece in accordance with the clock signal on the basis of the inversion flag.