Semiconductor memory with access protection scheme
A memory, particularly but not limitatively a flash memory, comprises at least one data storage area comprising a plurality of data storage locations, and an access circuitry for accessing the data storage locations for either retrieving or altering a data content thereof, depending for example on a memory user request. The memory includes at least one first user-configurable flag element and a second user-configurable flag element. Both the at least one first and the second flag elements are used by a user to set a protected state of the respective data storage area against alteration of the content of the data storage locations thereof. The protected state defined by setting the first flag element is user-removable, i.e., it can be removed by request from the user, so as to enable again the alteration of the content of the data storage area. On the contrary, the protected state defined by setting the second flag element is permanent and, once set, it cannot be removed: the data storage area becomes unalterable.
1. A memory comprising:
at least one data storage area comprising a plurality of data storage locations;
an access circuitry for accessing the data storage locations for retrieving or altering a data content thereof; and
at least one first user-configurable flag element and a second user-configurable flag element associated with said storage area, the first and second flag elements being used to define a protected state of the data storage area against alteration of the content of the data storage locations thereof, the protected state defined by the at least one first flag element being user-removable, while the protected state defined by the second flag element being permanent and non-removable,
in which the at least one first flag element has a first state and a second state, in which any alteration of the data content of the respective data storage area is allowed and, respectively, inhibited, and
the second flag element has a first state and a second state, in which changing of the state of the second flag element from the second state to the first state is allowed and, respectively, inhibited, so that when the second flag element is in the second state the respective data storage area is permanently protected against alteration of the data content thereof.
2. The memory of claim 1 , in which said second flag element can be set to define the permanent protected state of the respective data storage area irrespective of the fact that the at least one first flag element is set to define the removable protected state.
3. The memory of claim 1 , in which the at least one first flag element comprises a non-volatile programmable and erasable storage element, and the second flag element comprises a one-time programmable non-volatile storage element.
4. The memory of claim 1 , in which the second flag element can be set into the second state only if the at least one first flag element is in the second state.
5. The memory of claim 1 , in which said at least one storage area comprises at least two storage areas, and in which for each of said at least two storage areas a respective first and second user-configurable flag elements are provided.
6. The memory of claim 1 , comprising at least one further data storage area comprising a plurality of storage locations, and user-configurable flag means associated with said at least one further data storage area adapted to define a protected state of the at least one further data storage area against the alteration of the content of the respective storage locations, said protected state being removable by the user and not permanent.
7. The memory of claim 1 , comprising means for conditioning the configuring of said first and second flag elements by the user on the recognition of the user by the memory.