Mitsubishi Denki Kabushiki Kaisha

Seiichiro Asari

Koichi Kawauchi

A nonvolatile semiconductor memory device includes rewritable areas (M10, M20). A control circuit (110) controls a boosting circuit (2) and a writing circuit (10) such that a high voltage is generated from the boosting circuit, and data is written to the rewritable area designated by an address register/decoder (104) by means of the writing circuit. In response to an external signal which is at the 'H' level, the control circuit allows writing of data to the rewritable areas (M10, M20) by means of the writing circuit (9). In response to an external signal which is at the 'L' level, the control circuit prohibits rewriting of data in the rewritable area (M10), and allows rewriting of data in the rewritable area (M20). Therefore, even if the operation mode is erroneously set to the write mode because of unstable state of the power supply, data in the rewritable area is not destroyed.

Non-volatile semiconductor memory device with timer controlled re-write

A non-volatile semiconductor memory device comprises an area in which only one rewriting is possible and an area in which rewriting is possible repeatedly. A control circuit generates a high voltage from a boosting circuit and operates a writing circuit to write data in the rewritable area whose address designated by an address register/decoder. The control circuit allows writing of data into the area in which only one rewriting is possible by the writing circuit in response to an external signal. Therefore, even if the writing mode is set influenced by the unstable state of the power supply, destruction of the data in the area in which only one rewriting is possible can be prevented.

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Hyogo, Japan

Seiichiro Asari