An image forming device is provided. The device includes a main body (100) which includes a main controller (110) controlling operations of the image forming device, a consumable unit (200) mounted on the main body to enable communication with the main controller, and a CRUM chip (210) which is provided in the consumable unit and stores usage information of the consumable unit and characteristics information. The main controller and the CRUM chip transmit and receive signals which include data and integrity detection data between each other. The integrity detection data is generated by accumulating and reflecting integrity detection data included in a previous signal.