| 摘要 |
PURPOSE:To protect a memory content, by making ineffective rewrite of the content of a backup memory in the specific state. CONSTITUTION:At normal operation, the main power supply 2 is fed to the electronic desk top function 1 through the main power supply switch 7 to realize basic function as the electronic desk top calculator. In rewriting the content of the backup memory 5, although the write-in signal is output on the signal line 8, since the output of the state set section 3 is connected to an AND gate 4, the rewrite is enable only when the state of the output 9 is at ''1'', and the value of the signal line 8 is output to the signal line 10. On the other hand, when the state of the output 9 is at ''0'', the gate 4 is closed and the signal on the signal line 8 is not delivered. The memory exclusive power supply 6 is coupled to the backup memory 5. |
