| 摘要 |
<p>PURPOSE:To restrict the influence of a miswriting only to a specific address by outputting the specific address from an address switching part during the detection of OFF of a main power supply by a main power supply OFF detecting part. CONSTITUTION:When the main power supply 1 is OFF, a VCC-OFF signal outputted from a main power supply OFF detecting part 31 is turned to an H level. Thereby the address outputs A0-AN of an address switching part 32,a chip select signal CS from a data holding control part 33 and a memory writing signal W are respectively turned to the H levels respectively through OR circuits 32A, 32B, 33A, 33B. During the OFF of the main power supply, an address output to a memory 4 is fixed on the H level. Thus, the area of the memory 4 can be utilized at an optional ratio by selecting the number of OR circuits constituting an address switching part 32.</p> |
