Semiconductor integrated circuit device having improved input/output interface circuit

A semiconductor integrated circuit device includes an external terminal (17, 140), an internal logic circuit (110), and an input/output interface circuit (120, 130). The input/output interface circuit includes an input circuit (7), a selection circuit (10) and an output circuit (8). The input circuit (7) receives an input signal and supplies the internal logic circuit (110) with the same. The selection circuit (10) selects either the input signal supplied from the input circuit (7) or an output signal supplied from the internal logic circuit (110). The output circuit (8) outputs the selected one of the input signal and output signal to the external terminal. A loop circuit is formed by the input circuit (7), selection circuit (10) and output circuit (8). The loop circuit logically includes an odd number of inverters.