| 摘要 |
PURPOSE:To avoid such a case where data are mistakenly rewritten by a misoperation, etc., by writing the constant of a controller into a prescribed writing area of a read/write enable memory which designates a writing area via a digital circuit and is never erased even though a power supply is cut off. CONSTITUTION:A writing operation is carried out to a memory 2 for an area designating/writing signal via a digital circuit based on a writing indication signal as well as a writing area designating signal. Thus it is possible to avoid such a case where the write data are changed by a misoperation or abnormality of a microprocessor 1 unlike a conventional case where the writing operation is carried out based on a program. At the time of reading the constant data, a microprocessor 1 outputs the output of a relevant address via an address bus 10. Then the memory 2 outputs the contents of the corresponding address via a data bus 20 in a period when an access request signal -MR indicating a reading operation is set at L.
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