| 摘要 |
<p>PURPOSE:To perform a highly accurate erasing operation in a short time by providing an automatic control circuit performing pre-writing, high speed erasing, write-in, low speed erasing successively. CONSTITUTION:An automatic control circuit 15 to which a write-in control signal or an erasing control signal is inputted through a command decoder 14, performs sequence control operation required for erasing operation or write-in operation. That is, an erasing mode is started, pre-writing and pre- verifying are performed. And erasing operation is performed en bloc and at a high speed with a comparatively large erasing reference voltage, and erasing verifying is performed. Further, the batch erasing is performed in a comparatively long time with a comparatively low erasing reference voltage, and erasing verifying is performed. Thereby, threshold voltage by which an erasing state can be obtained in a short time and highly accurately can be set.</p> |
