| 摘要 |
<p>PROBLEM TO BE SOLVED: To protect existent data in a nonvolatile semiconductor memory by setting the protecting function of data in the nonvolatile semiconductor memory. SOLUTION: In order to prohibit the erasing and rewriting of data in a flash memory 12, the terminal 13 of a portable telephone set 11 and the connector of a protect setting device 14 are connected to each other. Then a data protecting signal is outputted from the protect setting device 14 to the portable telephone set 11. The protect setting device 14 prohibits the flash memory 12, which inputs these data protecting signals, from the erasing and writing of data. Concretely, as the terminal voltage of an address and that of output enable become twice as high as those at the time of normal operation, a voltage output circuit outputs the voltage detection signal of a level 'H' to a control circuit. Then the control circuit writes an erasing/writing prohibiting information to a part of the flash memory 12. Thereby an erasing circuit and a writing circuit stops operation while setting the data protecting function.</p> |
