A display device communicating with a microcontrol unit by data, including: a panel with a plurality of pixels; and a display driver operating to drive the panel, in which the display driver includes: a data bus with a plurality of widths; a register storing an index and parameter input from the microcontrol unit through the data bus; and a bus width control circuit selecting one of the plurality of widths with reference to the index and parameter stored in the register and conducting data communication with the microcontrol unit by means of the selected bus width. An index or parameter is introduced for transferring information to configure a data bus width, so that it is possible to reduce the number of mode set pins for determining the data bus width.