| 摘要 |
PURPOSE:To prevent the erasion of data on a volatile semiconductor memory part before it is rewritten by closing a switch to transfer the data stored in the volatile semiconductor memory to a sense amplifier before the data on a nonvolatile semiconductor memory part is rewritten and then opening the switch. CONSTITUTION:When a switch 7 is closed before the data on a nonvolatile semiconductor memory part 4 is rewritten, the data stored in the volatile semiconductor memory parts 2 and 3 are transferred to a sense amplifier 6 and temporarily latched there. Then when the switch 7 is opened, the data on the part 4 is rewritten regardless of the type of the data. When the data rewritten and latched by the amplifier 6 is transferred to the volatile semiconductor memory parts 2 and 3 respectively, the data on both parts 2 and 3 are set in the states secured before the data on the part 4 is rewritten. As a result, the unrewritten data on the parts 2 and 3 are never erased. |
