MICROCOMPUTER TEST SYSTEM

PURPOSE:To perform the internal check of a ROM part by using a means which is started in an action mode where no access is given to the ROM part and then changed automatically to another action mode to give an access to the ROM part. CONSTITUTION:A resetting action is given when a test is started and therefore an instruction is read out of a start address of a ROM 13 and loaded to a CPU 11. The address 14 has a jump instruction and a jumping designation address is stored in a RAM 12 or an area of an external memory where a ROM test routine 15 is stored for the ROM 13. The routine 15 indicates the change of action modes to a mode changing circuit 16. When the action mode is changed, an access is possible to the ROM 13 from a CPU 11. Then the contents of the ROM 13 are successively read outside by the subsequent instructions of the routine 15 and checked.