| 摘要 |
PURPOSE:To change a microcode without complicating a system by arranging memories to be rewritten/erased in order to change a microcode in a mask ROM in the seam address space, and while considering the degree of integration and economical efficiency, integrating these memories so as to optimize respective factors. CONSTITUTION:In a system controlled by a microcode, the mask ROM storing the microcode and the rewritable/erasable memory for writing a corrected microcode when the change of the microcode in the ROM 3 is required are arranged on the same address space of the same chip, a RAM 2 is also mounted on the same chip, and the storage capacity values of respective memories are determined and integrated so that the degree of integration and the economical efficiency are considered and optimized. Consequently, the microcode stored in the mask ROM 3 can be changed by converting the memory into a non- volatile memory and then writing the microcode therein, so that it is unnecessary to write the microcode in the area of the RAM 2 every time a power source is turned on.
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