An object of the present invention is to provide a memory system that offers enhanced security of ROM code that is data whose contents can be utilized for a given purpose in its intact form. In a memory system, data is read from a memory according to at least two or more addresses outputted from an address generator, from individual pages uniquely specified respectively by the addresses. A data generator generates one piece of data on the basis of the at least two or more pieces of data read from the individual pages.