Abstract: A technique for collectively setting a factory mode of operation of a monitor offers adjustments or modifications for particulars of mode data to meet user requirements, by transmitting a set of factory mode timing data from an external controller to an electrically erasable programmable read only memory using a serial interface data communication. A factory mode data transmission process includes the steps of transmitting a start data signal to a microcomputer in a monitor when a storage key input is fed to the external controller, repeatedly sending the timing data until a mode end signal is input and sending a mode end data to the microcomputer when a mode end signal is input. In addition, a factory mode data receiving process includes the steps of sending back the start data received to the external controller, storing mode timing data received into a factory mode address reserved in a memory in the monitor and ending the reception of mode timing data when mode end data is inputted.