PURPOSE: To use and select as two types of memories of an ECC circuit incorporating type of non-incorporated type by providing a means for selecting and controlling a function of the ECC circuit provided on a memory chip to a valid condition or to an invalid condition in accordance with the result detecting whether an ECC circuit selecting signal is impressed to an external terminal or not.

CONSTITUTION: There is provided an ECC circuit selecting signal detecting circuit 5 for detecting whether an ECC circuit selecting signal is impressed or not within a fixed period in an external terminal 1. There is provided an ECC function selecting control means 6 that in accordance with an output signal of this detecting circuit 5, a connecting condition of an ECC circuit and a memory circuit 3 is changed over and controlled to a valid or an invalid condition. As enbodiment of this selecting control means 6, a switch circuit for selecting and controlling the circuit connection of the ECC circuit 4 and the memory circuit 3 may be disposed, or a part of gates in the ECC circuit 4, for example, a parity inspection result data inputting AND gate 39 in a correction data producing circuit 37 may be changed so as to perform a gate control by an ECC function selecting control signal from the ECC circuit selecting signal detecting circuit 5.