Abstract: A semiconductor integrated circuit comprises a digital circuit for performing a signal process and producing a digital signal, a digital/analog converter for converting the digital signal produced by said digital circuit into an analog signal, and logic means for extracting a predetermined number of bits from the digital signal upon a test mode. The semiconductor integrated circuit further comprises a switching circuit for selecting either one of the digital signal from said digital circuit and the analog signal from said digital/analog converter on the basis of a non-test mode or test mode, and for providing an external circuit with a selected signal, and a test controlling circuit for designating either one of said test and non-test modes and providing said logic means and switching circuit with a mode signal.