Semiconductor device with double program prohibition control
The present invention provides a semiconductor device and a method for controlling the semiconductor device, the semiconductor device including memory regions; program prohibition information units storing program prohibition information to be used for determining whether to prohibit or allow programming in the memory regions corresponding to the program prohibition information units; a first prohibition information control circuit that prohibits a change of the program prohibition information from a program prohibiting state with respect to a memory region based on first prohibition information; and a second prohibition information control circuit that prohibits a change of the program prohibition information from a program allowing state to a program prohibiting state with respect to the corresponding memory region based on second prohibition information with respect to the corresponding memory region.
1. A semiconductor device comprising:
a memory cell array comprising a plurality of memory regions;
a plurality of write protect content addressable memories (WPCAMs) corresponding to the plurality of memory regions and containing program prohibition information used to determine whether programming in a corresponding memory region is prohibited or allowed;
a plurality of content addressable memories (CAMs) including a first CAM and a second CAM, the plurality of CAMs being configured to contain prohibition information used to determine whether changing the program prohibition information in a WPCAM is prohibited or allowed;
a write protected content addressable memory (WPCAM) control circuit, configured to reference prohibition information contained in the plurality of CAMs and operable to prohibit a change of the program prohibition information in a WPCAM based on the prohibition information; and
a program control circuit configured to program the plurality of memory regions,
wherein the WPCAM control circuit receives as input a WPCAM command and prohibition information from the first CAM to prohibit or allow programming of a WPCAM of the plurality of WPCAMs,
further wherein the program control circuit is configured to prohibit or allow programming a memory region based on the program prohibition information contained in the WPCAM corresponding to the memory region.
2. The semiconductor device according to claim 1 , wherein the WPCAM control circuit comprises a plurality of prohibition information control circuits including a first prohibition information control circuit and a second prohibition information control circuit, the plurality of prohibition information control circuits being operable to receive prohibition information from the CAMs and prohibit or allow writing and erasing to the WPCAMs based on the prohibition information received from the CAMs.
3. The semiconductor device according to claim 2 , wherein the first prohibition information control circuit is configured to read prohibition information from the first CAM and to prohibit erasing in a WPCAM unless a WPCAM erase signal is received as input and the first prohibition information corresponds to an erase state.
4. The semiconductor device according to claim 3 , wherein the first prohibition information control circuit comprises a first switch, wherein erasing in a WPCAM is allowed only when the first switch is turned on.
5. The semiconductor device according to claim 4 , wherein the first switch is turned off when the prohibition information in the first CAM corresponds to a write state, and turned on when the prohibition information in the first CAM corresponds to an erase state.
6. The semiconductor device according to claim 5 , wherein the first switch is turned off when the prohibition information in the first CAM corresponds to a write state, and turned on when the prohibition information in the first CAM corresponds to an erase state, regardless of the prohibition information in the second CAM.
7. The semiconductor device according to claim 2 , wherein the second prohibition information control circuit is configured to read prohibition information from the second CAM and to prohibit writing to a WPCAM unless a WPCAM write signal is received as input and the second prohibition information corresponds to an erase state.
8. The semiconductor device according to claim 7 , wherein the second prohibition information control circuit comprises a second switch, wherein writing in a WPCAM is allowed only when the second switch is turned on.
9. The semiconductor device according to claim 8 , wherein the second switch is turned off when the prohibition information in the second CAM corresponds to a write state, and turned on when the prohibition information in the second CAM corresponds to an erase state.
10. The semiconductor device according to claim 9 , wherein the second switch is turned off when the prohibition information in the second CAM corresponds to a write state, and turned on when the prohibition information in the second CAM corresponds to an erase state, regardless of the prohibition information in the first CAM.
11. The semiconductor device according to claim 1 , wherein the plurality of WPCAMs are disposed on a plurality of p-type wells.
12. The semiconductor device according to claim 1 , wherein the plurality of CAMs are disposed on a plurality of p-type wells.
13. The semiconductor device according to claim 1 , wherein the plurality of CAMs are disposed on a different plurality of wells from the wells upon which the WPCAMs are disposed.
14. The semiconductor device according to claim 1 , wherein the first CAM is disposed on a different well from the well upon which the second CAM is disposed.
15. The semiconductor device according to claim 1 , wherein the semiconductor device comprises a flash memory device.