PURPOSE: To improve the utilizing efficiency of an AND-OR constitution section by separating the AND-OR constitution section and an input/output buffer section so as to be connected optionally thereby eliminating the limitation to number of input/output pins.

CONSTITUTION: A programmable switch is provided at each cross point between an input line 8 and a metal line 6 of AND-OR constitution blocks 2-1∼2-3 and a programmable switch is provided to each cross point between an output line 10 and the metal line 6. Further, a programmable switch is provided to each cross point between the input line 12 and the metal line 6 of input/output buffer blocks 4-1∼4-12 and a programmable switch is provided to each cross point between an output line 14 and the metal line 6. A programmable switch 16 is provided to the metal line 6 so as to be split at a proper location for the connection between any of the AND-OR constitution blocks 2-1∼2-3 and any of the input/output buffer blocks 4-1∼4-12.