| 摘要 |
<p>PURPOSE: To enhance the data erasure characteristics of EEPROM by controlling the magnitude of data erasure voltage for each memory cell depending on the current flowing through the bit, line of a nonvolatile memory. CONSTITUTION: In an EEPROM, a read voltage is applied in order to convert the current flowing on a bit line 8 into a voltage through a sense amplifier 12. The voltage indicative of the current is then converted through an AD converter 13 into a digital value. An operational logic unit 18 compares the digital output from the AD converter 13 with a value read out from a ROM. When a logical operation output indicative of unmatching is delivered from the unit 18 to a decision section 17, count in a program counter 16 is altered to match with an output read out from a mask ROM 15. Consequently, a matched output data is delivered from the unit 18, the count in the counter 16 is altered, a table data is read out from the ROM 15, a corresponding control bit is set in a register 20 and negative charges in an MOS transistor 6 are offset.</p> |
