PURPOSE: To reduce noise to be generated, to decrease the change points of respective bits and to reduce energy consumption by converting continuous codes to codes changing only one bit, and outputting those codes to an address bus.

CONSTITUTION: A code converter 7 is provided in a microcomputer 1 while being connected to a binary counter 6, converts continuously increasing/ decreasing binary codes composed of plural bits showing numerical display from the binary counter 6 to the codes differing the bit signals of bit positions between the two codes continuing the numerical display and outputs the codes to an address bus 3. Thus, since the code converting means is provided in the microcomputer, the codes outputted from the microcomputer to the address bus differ the bit signals of the bit positions between the two codes continuing the numerical display. Therefore, the plural bits are not simultaneously changed on this address bus as long as the continuous addresses are accessed.