A display driver, a display unit, and an electronic instrument that enables the simultaneous display of a still image and a moving image on the same scan line. An X driver IC includes at least display data RAM, in which is stored still-image data for one frame, and a line memory, in which is stored moving-image data for one scan line. A selector circuit selects one of still-image data for one scan line in the horizontal direction, which is read from the display data RAM, or moving-image data for one scan line, which is read from the line memory, based on image determination data, and outputs it as composite data of a still image and a moving image, for each column position. After the composite data has been latched by an output latch circuit, a liquid crystal panel is driven based on the latched data by a liquid crystal drive circuit.