System for performing writes to non-volatile memory elements in a minimal time

摘要

A single chip type microcomputer includes at least a central processing unit (CPU), a random-access memory (RAM), a mask read-only memory (mask ROM) and an electrically writable ROM such as an electrically erasable and programamble read-only memory (EEP-ROM). The electrically writable ROM stores both the user program and data to be preserved. The microcomputer includes further memory for storing a write control program for controlling the write operation to the writable ROM, and the electrically writable ROM and the memory are disposed to mutually different address positions on the address space of CPU. The proportion of size of the user program region and the data region in the writable ROM can be selected in a free proportion. A timer governs writes to the writable ROM.