| 摘要 |
<p>PURPOSE:To exactly protect the stored content of an EPROM cell array from a third person by inhibiting a person except for a specific person who knows the content of data stored in the EPROM cell array from reading the data of the EPROM cell array, and reloading the content of the EPROM cell array when the third person inputs the erroneous data. CONSTITUTION:The above circuit is equipped with a control circuit 2 which generates a write pulse WP when a write signal WE is applied, and generates the pulse WP after generating a read pulse RP when a read signal RE is applied. Also, the circuit is equipped with a comparator circuit 3 which compares data DTR from an EPROM cell array 1 read by the read pulse RP with data DTI from an outside, and outputs a match signal EQ in an active level only when they are matched. A reading inhibiting circuit 4 outputs the data DTR from the EPROM cell array 1 only when the match signal EQ is in the active level. The EPROM cell array 1 rewrites the data DTI from the outside by the writing pulse WP after operating the reading.</p> |
