| 摘要 |
PURPOSE:To make it unnecessary for software to recognize the duplication of a file by operating an in-operation system memory part, a standby system memory part and a semiconductor memory part provided with a control part according to a specific instruction from a central processing unit. CONSTITUTION:The semiconductor memory device is equipped with the in- operation system memory part 300, the standby system memory part 400 and the control part 200. According to the indication from the central processing unit the in-operation and standby system memory parts 300 and 400 are simultaneously selected and caused to execute the same action. When the standby system memory part 400 develops a trouble, the selection of the standby system memory part 400 is separated, and the fact that the standby system memory part 400 develops the trouble is reported to the central processing unit. Afterward, only the in-operation system memory part 300 is used until the trouble of the standby system memory part 400 is removed.
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