a semiconductor integrated circuit capable of changing a product specification comprises a first circuit section having a first function , a second circuit section having a second function , and active signal generator means for producing an active signal for activating either the first circuit section or the second circuit section . to change the product specification , the integrated circuit further comprises means for receiving a decision signal , switching signal generator means , connected to said receiving means , for producing a switching signal for changing the product specification according to the decision signal , and switching means for receiving the active signal and the switching signal and for supplying the active signal to either the first circuit section or the second circuit section according to the switching signal .