MICROCOMPUTER HAVING P-ROM BUILT-IN

摘要

PURPOSE:To facilitate the analysis of the P-ROM data against the occurrence of a fault while keeping the security of secret to the outsiders for a microcomputer which contains a P-ROM having its verifying inhibition protection mode. CONSTITUTION:A microcomputer contains a protection information memory cell 2 consisting of a P-ROM cell, a protection decoder 20 which inputs and decodes the data on the cell 2, and an address modifying circuit 4 which modifies the address information on a P-ROM in a verifying mode of the P-ROM with the output signal of the decoder 20. The decoder 20 consists of a logic circuit which excludes the combination of two different types of data and becomes active only when the data except those combined data are inputted.