Patent ID: 7770027

Claim:
A semiconductor memory device removably mountable to an information processing apparatus, said semiconductor memory device comprising: a memory core section structured to store therein data including a program to be protected, said memory core section including an address input section and a data output section; an input/output terminal section including command input terminals structured to receive a command including an instruction code and address data from said information processing apparatus, and data output terminals arranged to provide data read from said memory core section to said information processing apparatus; and a memory control section connected between said memory core section and said input/output terminal section, wherein said memory control section includes a command decryption circuit arranged to be selectively operative to decrypt the command provided to said command input terminals or to output the command without processing, a scrambling circuit structured to be selectively operative to scramble the data read from said memory core section or to output the data without processing, a command judgment circuit structured to judge whether the command provided from said information processing apparatus is a first command specifying a transition to a first operating mode or a second command specifying a transition to a second operating mode, an operating mode control circuit structured to select the first operating mode for enabling a command decryption function of said command decryption circuit in response to a judgment made by said command judgment circuit that the command is the first command, and structured to select the second operating mode for enabling a scrambling function of said scrambling circuit in response to a judgment made by said command judgment circuit that the command is the second command, and a descrambling circuit arranged to be selectively operative to pass the command provided to said command input terminals without processing therethrough or descramble the command, and wherein said operating mode control circuit disables a descrambling function said descrambling circuit when said first operating mode is selected.