| 摘要 |
<p>PURPOSE:To erase stored data precisely within the shortest period by repeatedly checking data erasing during the irradiation of ultraviolet rays. CONSTITUTION:An erasing detection circuit 3 detects whether stored data to be erased from an EPROM 9 have been already erased or not. When the data have been erased, the output data of a counting circuit 6 are latched and trebled to use the trebled data as comparing data of a comparator 5 and the output data of the counting circuit 6 are directly inputted to the comparator 5 as the data to be compared. When the relation between the data N' to be compared and the comparing data 3N is N'>=3N, a comparator 5 lights up an erasing end displaying unit 8. When erasing can not be detected by the initial operation of the circuit 3, a lighting circuit 2 for lighting up an ultraviolet lamp 1 is driven to irradiate ultraviolet rays on the EPROM 9, and simultaneously an oscillator 7 oscillates and the counting circuit 6 executes counting operation. Said operation is repeated until the erasure of the EPROM 9 can be detected by the circuit 3.</p> |
