Patent ID: 6201742
Filing Date: 2001-03-13
Classification: G11C

Abstract:
A circuit that prevents illegal transformation of data in a non-volatile memory, said circuit comprising:a current generation circuit which generates a first, second and third reference current as reference currents for comparison with a cell current which cell current is the current read from a cell of said non-volatile memory, wherein the second reference current is larger in magnitude than the first reference current and the third reference current is smaller in magnitude than the first reference current;a comparison circuit which compares the magnitude of the cell current with the magnitude of each of the first to third reference currents;a writing/deletion circuit which writes data in or deletes data from the cells of said non-volatile memory; anda control circuit which outputs an information regarding presence or absence of charge in a target cell based on the result of comparison by said comparison circuit, and makes said writing/deletion circuit execute writing data in or deletion of data from a target cell of said non-volatile memory once more when the conditions that the cell current is not greater than the second reference current or the cell current is greater than the third reference current are satisfied.