Non-volatile memory data protection
First Claim
1. A write-protected memory, comprising:
- an addressable memory array including a plurality of memory cells;
a plurality of toggle flags each associated with each one of said memory cells;
a special-write input for controlling a direct writing of data to each of said memory cells; and
a normal-write input for conditionally writing data to each of said memory cells dependent on a pristine state of a corresponding one of the plurality of toggle flags;
wherein, data is prevented from being written into any of said plurality of memory cells by the normal-write input if said corresponding one of the plurality of toggle flags is not in a pristine state.
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Accused Products
Abstract
A write-protected memory device has two write modes. Such memory device has many memory cells organized into pages. A normal write mode checks a one-bit flag collocated with every memory cell to see if writes are allowed. If the flag indicates a write operation to that memory cell is allowed, the flag is toggled and the cell is written. If the flag has previously been toggled, the write operation is prevented. A special write mode allows write operations to memory cells regardless of the state of the one-bit flag. The special write mode can be discerned in hardware by the loading of a register with a reprogrammable password, or the splitting of a normal single write-enable pin into two independent pins, e.g., normal write and special write. The memory operations can proceed either in page mode or cell-by-cell
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Citations
7 Claims
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1. A write-protected memory, comprising:
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an addressable memory array including a plurality of memory cells;
a plurality of toggle flags each associated with each one of said memory cells;
a special-write input for controlling a direct writing of data to each of said memory cells; and
a normal-write input for conditionally writing data to each of said memory cells dependent on a pristine state of a corresponding one of the plurality of toggle flags;
wherein, data is prevented from being written into any of said plurality of memory cells by the normal-write input if said corresponding one of the plurality of toggle flags is not in a pristine state. - View Dependent Claims (2, 3, 4, 5, 6, 7)
the special-write input is software accessible only, and requires the use of a special access codeword or password for writing said plurality of memory cells if said corresponding one of the plurality of toggle flags is not in said pristine state;
wherein, said special access codeword or password can be re-written so only a unique user can thereafter access a special write operation.
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Specification