In this paper, the software technique for driving dynamic display circuit using timer interrupt is proposed. As proposed technique makes the display software independent of main program, the algorithm of main software becomes simple. On the other hand, as display timing is fixed by the interrupt from timer circuit of micro-controller, the timing of switching becomes precise. In order to verify the effectiveness of proposed software technique, experimental circuit is designed as Timer Interrupt generator into the 4 MHz micro-controller. Experimental results show that proposed software technique controls switching digits of 7-segment exactly, and main software algorithm become very simple.