Nonvolatile semiconductor memory device having protection function for each memory block

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, when the erase command is input from the interface, the erase circuit executing the erase command when a protect flag in the selected memory block has a first value and not executing the erase command when the protect flag has a second value; and

a read circuit which reads, in accordance with the address input to the interface, the protect flag that is stored in a part of the selected memory block, the protect flag read by the read circuit being able to be output to the external device through the interface.

2. A device according to claim 1 , wherein the protect flag is stored in a plurality of memory cells in each memory block, and when the protect flag is read, error correction is executed in accordance with a majority theory.

3. A device according to claim 1 , further comprising a write circuit which writes the protect flag in the part of the selected memory block in accordance with the address and a protect flag write command input to the interface.

4. A device according to claim 1 , wherein each of said plurality of memory blocks includes a plurality of NAND-type memory units.

5. A device according to claim 4 , wherein each of said plurality of NAND-type memory units include a plurality of memory cells connected in series.

6. A device according to claim 1 , wherein each of said plurality of memory blocks includes a plurality of pages, an erase operation is executed in units of blocks and a read/write operation is executed in units of pages.

7. A device according to claim 6 , wherein the protect flag is stored in a first page of said plurality of pages.

8. A device according to claim 1 , wherein:

each of said plurality of memory blocks includes a plurality of NAND-type memory units each including a plurality of memory cells connected in series;

each of said plurality of memory blocks includes a plurality of pages, an erase operation is executed in units of blocks, and a read/write operation is executed in units of pages;

the protect flag is stored in a first page of said plurality of pages.

9. A device according to claim 1 , wherein

each of said plurality of memory blocks includes a plurality of pages, an erase operation is executed in units of blocks, and a read/write operation is executed in units of pages, and

the protect flag is stored in a last page of said plurality of pages.

10. A device according to claim 9 , wherein the protect flag is stored in a plurality of memory cells in each memory block, and when the protect flag is read, error correction is executed in accordance with a majority theory.

11. A device according to claim 9 , wherein further comprising a write circuit which writes the protect flag in the part of the selected memory block in accordance with the address and a protect flag write command input to the interface.

12. A device according to claim 9 , wherein each of said plurality of memory blocks includes a plurality of NAND-type memory units.

13. A device according to claim 12 , wherein the each of said plurality of NAND-type memory units includes a plurality of memory cells connected in series.

14. A device according to claim 1 , wherein

each of said plurality of memory blocks includes a plurality of NAND-type memory units each including a plurality of memory cells connected in series;

each of said plurality of memory blocks includes a plurality of pages, an erase operation is executed in units of blocks, and a read/write operation is executed in units of pages; and

the protect flag is stored in a last page of said plurality of pages.