disclosed herein is a discharge lamp lighting device which realizes the minute control of the lighting sequence and electric power of a high - pressure discharge lamp and the control of various anti - error protecting functions by mounting a microcomputer . however , since microcomputer processing typically progresses in accordance with the programs previously recorded on a rom , various actions of the discharge lamp are controlled in accordance with rom - recorded data settings . to modify these settings , the contents of the rom need to be updated . therefore , a function for communicating with an external device is assigned to the microcomputer so that various data settings can be modified .