Title:
SEMICONDUCTOR STORAGE DEVICE
Document Type and Number:
Japanese Patent JP3734408
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To obtain a non-volatile semiconductor storage device in which alteration of data is prevented, a security releasing key is hard to decode, repeating attack for certification by an illegal user can be suppressed.
SOLUTION: A security releasing key is stored in a memory region 12 in a block 11, a security register lock corresponding for each block is stored in a non-volatile register 13. Both are compared and verified by a security release discriminating circuit 4, when both are coincident, a data output permitting circuit 16 permits outputting a regular data. At the time of rewriting data, a security release key in the memory region 12 also is erased by block erasure, the security release key is written again in the memory region 12 after write-in of update data to release restriction for read-out. When an unauthorized user who does not know a correct security key rewrites data, data cannot be read out, a system cannot be used.
Inventors:
Ichiro Tomohiro
Application Number:
JP2000201650A
Publication Date:
January 11, 2006
Filing Date:
July 03, 2000
Export Citation:
Assignee:
Sharp Corporation
International Classes:
G11C16/02; G06F12/14; G06F21/10; G06F21/60; G06F21/62; G06F21/64; G11C16/22; (IPC1-7): G11C16/02; G06F12/14
Domestic Patent References:
JP2000112824A | ||||
JP3296842A | ||||
JP10134586A |
Attorney, Agent or Firm:
Hidesaku Yamamoto
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