WRITE SYSTEM OF WRITABLE READ ONLY MEMORY ELEMENT

摘要

PURPOSE:To confirm easily a non-operating area by setting an area storing a flag representing the presence or absence of data write corresponding to a word address to a part of a storage area of a PROM to set and store the flag to a flag area corresponding to every execution of data write thereby reading the flag area. CONSTITUTION:A PROM2 is written while being added with a flag by a write control section 15 at data write of a storage section 12 so as to set the flag to ''1'' at the presence of write data and to set the flag to ''0'' at the absence of write data in a word address code +1 flag corresponding to the write data in a data storage area. A main control section 11 allows the write control section 15 to access a code area of the PROM2 as the pre-processing at the write and allows a data comparison detecting section 16 to recognize the non-operating area. As a result, since the non-operating area is discriminated without applying read check as to the alreadly written data in the storage area of the PROM2, additional write with good efficiency is attained.