herein disclosed is a digital semiconductor integrated circuit which is equipped with : a digital signal input circuit ; an analog signal input circuit made receptive of an analog signal for feeding out a digital signal corresponding to said analog signal ; and a common external terminal connected commonly with the input terminals of said digital signal input circuit and said analog signal input circuit . by the preparation with the use of a suitable switch circuit , the common external terminal can be used as either an analog signal input terminal or a digital signal input terminal . as a result , the number of the external output terminals required for the semiconductor integrated circuit can be reduced .