PURPOSE: To make it possible to test, rapidly and simply, functional property of a peripherally structured system, by including a comprehensive test program in a masked ROM and by giving this program a function to write into data storing/processing elements.
CONSTITUTION: A microcontroller 11 has a masked ROM 14, which includes a comprehensive test program and the like, and a microcontroller system 12, which enables the controller 11 to function, has data storing/processing elements 16 to 110. The test program included in the ROM 14 reads data stored in a static memory 16, a dynamic memory 17 and the like, and writes data into the memory 17 and the like. And a program written in one of the elements including the memory 17 is executed. Efficacy of respective elements composing the system 12 can be thereby tested irrespetively of application programs. Further, a remote-loading program can be loaded in the memory 17 by changing an application program.