Nonvolatile semiconductor memory device having protection function for each memory block
View Patent ↗A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.
1. A nonvolatile semiconductor memory device comprising:
a plurality of memory blocks constituted by electrically programmable nonvolatile semiconductor memory cells;
a memory cell array constituted by the plurality of memory blocks;
an interface that communicates with an external device;
an erase circuit to erase data in a selected memory block in accordance with an address and an erase command input to the interface, the erase circuit reading an erase protect flag of the selected block before the data of the selected block is erased, executing the erase command when the erase protect flag has a first value, and not executing the erase command when the protect flag has a second value; and
a write circuit to write the erase protect flag in the selected memory block in accordance with the address and an erase protect flag write command input to the interface.
2. A device according to claim 1 , wherein the erase protect flag is stored in a plurality of memory cells in each memory block, and when the erase protect flag is read, error correction is executed in accordance with a majority theory.
3. A device according to claim 1 , wherein the write circuit writes a write protect flag in the selected memory block in accordance with the address and a write protect flag write command input to the interface, and writes back the write protect flag after the erase command is executed.
4. A device according to claim 3 , wherein the write protect flag is stored in a plurality of memory cells in each memory block, and when the write protect flag is read, error correction is executed in accordance with a majority theory.
5. A device according to claim 1 , wherein each of the plurality of memory blocks includes a plurality of pages.
6. A device according to claim 5 , wherein the protect flag is stored in a first page of the plurality of pages.
7. A device according to claim 5 , wherein the protect flag is stored in a final page of the plurality of pages.
8. A device according to claim 5 , wherein the protect flag is stored in a middle page of the plurality of pages.
9. A device according to claim 6 , wherein the first page includes a plurality of byte areas and the protect flag is stored in last few byte areas of the first page.
10. A device according to claim 7 , wherein the final page includes a plurality of byte areas and the protect flag is stored in last few byte areas of the final page.
11. A device according to claim 8 , wherein the middle page includes a plurality of byte areas and the protect flag is stored in last few byte areas of the middle page.