Patent ID: 7281103

Claim:
A microcomputer comprising: a memory which stores a predetermined program; a CPU which reads the program stored in the memory based on a predetermined instruction to perform a predetermined calculation; a read controller which controls reading of the program from the memory; a plurality of memory areas which are a plurality of portions provided by dividing the memory and which each store respective programs being different from one another and having different distinction marks in the portions, respectively; a distinction unit that, by using different distinction codes that are internally generated from the predetermined instruction and included therein and by comparing the distinction mark of the memory area with the distinction code included in the predetermined instruction, distinguishes that a specified memory area having a certain distinction mark being consistent with a corresponding distinction code, is a memory area storing a program to be read; and a read access controller that, when the distinction unit distinguishes an agreement of the distinction mark and the distinction code, enables the reading of the program from the distinguished memory area, and when the distinction unit distinguishes a disagreement of the distinction mark and the distinction code, prohibits the reading of the program from the distinguished memory area in which the program is stored.