Secure microprocessor/microcomputer with secured memory

Claim 1

A data processing device formed on a single semiconductor substrate comprising: a central processing means for performing data processing operations upon data in accordance with instructions, said data processing operations including at least one memory access operation for recall of data or an instruction stored in a specified address location; a nonvolatile memory means having a plurality of address locations which are a first subset of the possible address locations of said at least one memory access operation, for storing data and instructions which define data processing operations at respective address locations; a temporary read-write memory means having a plurality of address locations which are a second subset of the possible address locations, said second subset including a secure set of address locations, for temporarily storing data and instructions which define data processing operations at respective address locations; an information transfer means connected to said central processing means, said nonvolatile memory means and said temporary read-write memory means for transfer of data and instructions; an external interface means connected to said information transfer means for providing information to at least one device external to said single semiconductor substrate; at least one security bit memory means disposed in proximity to said nonvolatile memory means, each for storing therein a single bit of data indicating a secure state when said nonvolatile memory means and said secure subset of memory locations of said temporary read-write memory means is to be secure or a nonsecure state; address logic means connected to said central processing means, said information transfer means and said at least one security bit memory means for generating a security signal when said security bit memory means indicates a secure state and said central processing means is performing a data processing operation in accordance with an instruction including a memory access operation to recall data as an operand which is stored in either said nonvolatile memory means and or in said secure set of address locations of said temporary read-write memory means; and an external interface inhibit means connected to said external interface means and said address logic means for inhibiting the transfer of data and instructions to the external device via said external interface means upon reception of said security signal.