PURPOSE: To obtain a semiconductor integrated circuit which does not require a self-controlling circuit, and also in which a load capacity of an external signal line is small, by providing plural switches connected between the external signal line and an external signal input terminal of each circuit block, so that each switch is controlled by an internal signal of each circuit block.

CONSTITUTION: When an internal signal ia has a high potential, a transistor Qsi becomes on, therefore, an external signal Ψ is inputted to a gate of an input transistor Qia and controls an operation of a circuit block (ia). On the other hand, when the internal signal ia has a low potential, the transistor Qsi becomes off, therefore, the level of the external signal Ψ at the time point when the internal signal ia falls to a low potential from a high potential is held in the gate of the input transistor Qia. This holding operation is released when the internal signal ia rises to a high potential. In this way, whether the level of the internal signal ia of each circuit block (ia) receives control to the circuit block (ia) by the external signal Ψ or not is determined.