Multi-bit-per-cell flash EEPROM memory with refresh

Details Multi-bit-per-cell flash EEPROM memory with refresh Multi-bit-per-cell flash EEPROM memory with refresh

2008-07-08

2008-07-08

Lam, David (Department: 2827)

Static information storage and retrieval

Floating gate

Particular connection

C365S185240, C365S222000, C365S189090

Reexamination Certificate

active

07397697

ABSTRACT:
A multibit-per-cell non-volatile memory divides the suitable threshold voltages of memory cells into ranges corresponding to allowed states for storage of data and ranges corresponding to forbidden zones indicating a data error. A read process checks whether a threshold voltage is in a forbidden zone. Alternately, a refresh process includes reprogramming the threshold voltage into an allowed state. In the case of a flash memory, a refresh reads a sector of the memory and saves corrected data from the sector in a buffer or another sector. The corrected data from the buffer or other sector can be written back in the original sector, or the corrected data can be left in the other sector with addresses of the original sector being mapped to the other sector. Refresh process for the non-volatile memory can be performed in response to detecting a threshold voltage in a forbidden zone or periodically.

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