Integrated microcontroller and memory with secure interface between system program and user operating system and application

Abstract

An integrated circuit device has a processing unit, a memory management unit, and a memory. The memory management unit is interposed between the memory and the processing unit for controlling access to the memory by the processing unit in one of three modes. In a first mode, called the system mode, the processing unit can access a system program stored in the memory for controlling the resources of the integrated circuit device. In a second mode, called the kernel mode, the processing unit can access an operating system program stored in the memory for controlling the of the integrated circuit device, limited by the system program. Finally in a third mode, called the user mode, the processing unit can access an application program stored in the memory for controlling the resources of the integrated circuit device, limited by the operating system program. In another aspect of the invention, when the processing unit accesses either the operating system program or the application program (herein: “non-system program”), the execution of the non-system program can cause a system interrupt causing program execution to revert to the system mode, but to a specified entry address of the system program, wherein after processing the system interrupt, operation returns to the non-system program in either the kernel mode or the user mode.

Dependencies are inferred from the claim text.