Patent ID: 8661553

Claim:
A semiconductor memory device for use with an electronic device, said semiconductor memory device comprising: a rewritable nonvolatile memory including a continuous area divided at a boundary address into an authentication area and a non-authentication area; and a control unit operable to control accesses by the electronic device to the authentication area and the non-authentication area in said rewritable nonvolatile memory; said control unit comprising: an authentication unit operable to check whether the electronic device has authority to access said semiconductor memory device, and affirmatively authenticate the electronic device when the electronic device has the authority; a command judgment unit operable to receive an instruction from the electronic device and to identify a command type of the instruction; an authentication area access control unit operable to access the authentication area according to the command type that said command judgment unit identifies from the instruction, only when said command judgment unit receives the instruction from the electronic device that said authentication unit affirmatively authenticates; and an area resizing unit operable to change the boundary address to a new boundary address to resize the authentication area and the non-authentication area only when said command judgment unit receives the instruction from the electronic device that said authentication unit affirmatively authenticates, and identifies the command type of the instruction as showing the new boundary address.