Semiconductor device and method of controlling the same

1. A semiconductor device comprising:

a memory cell array that includes non-volatile memory cells;

a first memory region and a second memory region that are located in the memory cell array, the first memory region being protected during a protecting period, the second memory region being not protected;

an address change circuit that changes an address in an address space of the first memory region and the second memory region in the memory cell array, to an address in an address space of the second memory region, during the protecting period; and

a control circuit that prohibits access to the first memory region, and allows access to the second region, during the protecting period.

2. The semiconductor device as claimed in claim 1 , wherein the address change circuit changes an external address that indicates the first memory region and is input to the semiconductor device, to an internal address that indicates the second memory region in the memory cell array.

3. The semiconductor device as claimed in claim 1 , wherein the control circuit allows access to the first memory region, when authentication data that is read from an authentication data storage region for storing the authentication data matches external authentication data that is input from the outside.

4. The semiconductor device as claimed in claim 1 , wherein the address change circuit does not change the address, when authentication data that is read from an authentication data storage region for storing the authentication data matches external authentication data that is input from the outside.

5. The semiconductor device as claimed in claim 2 , wherein the address change circuit changes a section address indicating a memory region to an address indicating the second memory region, but does not change an address in the memory region, the section address being an address in the memory cell array.

6. The semiconductor device as claimed in claim 5 , wherein the address change circuit changes a section address indicating the first memory region to a section address indicating the second memory region.

7. The semiconductor device as claimed in claim 1 , wherein the second memory region is a boot data region in which a system code or program is stored.

8. A method of controlling a semiconductor device that has a memory cell array including non-volatile memory cells, a first memory region that is to be protected during a protecting period, and a second memory region that is not to be protected, the first memory region and the second memory region being located in the memory cell array,

the method comprising the steps of:

changing an address in an address space of the first memory region and the second memory region in the memory cell array, to an address in an address space of the second memory region, during the protecting period; and

prohibiting access to the first memory region, and allowing access to the second memory region, during the protecting period.

9. The method as claimed in claim 8 , further comprising the step of

allowing access to the first memory region, when authentication data that is read from an authentication data storage region for storing the authentication data matches external authentication data that is input from the outside.

10. The method as claimed in claim 9 , wherein the address is not changed, when authentication data that is read from an authentication data storage region for storing the authentication data matches external authentication data that is input from the outside.