| 摘要 |
A bit symbol recognition method and a structure for multiple bit storage in a nonvolatile memory are provided to store information of a number of bits in a single EEPROM efficiently. In a nonvolatile memory device, a MOSFET(Q1) includes a storage layer storing charges indicating one of N different multi-bit words and a control gate(124). A source of the N multi-bit words indicates N different voltage levels in a digital type. A digital-analog converter(104) receives the N multi-bit words from the source sequentially, and provides N different voltage levels corresponding to the N multi-bit words to the control gate. An output buffer(102) receives the N multi-bit words. An output line carries a signal indicating the state of the MOSFET. A control circuit controls the output buffer to output a signal corresponding to the value of the multi-bit words indicated by the charges stored in the storage layer of the MOSFET, by supplying a signal to the output buffer, in response to the variation of the signal indicating the state of the MOSFET.
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