A semiconductor storage device includes a memory cell array and first and second circuits. The memory cell array is configured to store data in a non-volatile manner. The first circuit is configured to detect a first signal from an external device that is external to the semiconductor storage device. The first signal is required when the external device communicates with the semiconductor storage device in accordance with a first interface protocol, and not required when the external device communicates with the semiconductor storage device in accordance with a second interface protocol different from the first interface protocol. The second circuit is configured to generate a second signal in a first state when the first circuit detects the first signal and in a second state when the first circuit does not detect the first signal, the second state being different from the first state.