| 摘要 |
<p>PURPOSE:To optimize an erase time by monitoring the drain currents of storage blocks and by controlling the applying time of erase voltages to each of the storage block based on the monitored results. CONSTITUTION:Erase voltage applying means A1-Am, erase condition discrimination means B1-Bm and inhibiting means C1-Cm are provided for each of storage blocks D1-Dm which contain plural nonvolatile storage devices. And a prescribed potential of an erase voltage is applied to the source electrodes of nonvloatile storage devices, which have floating gates FGs, by the means A1-Am. When the drain currents ID of the nonvolatile storage devices become more than a prescribed current, the means B1-Bm judge the devices to become completely erased conditions and inhibit the voltage applying operations of the means A1-Am by the means C1-Cm. Having this arrangement, erase time of each block of the storage space which is divided into plural blocks is optimized.</p> |
