| 摘要 |
A memory management unit is disclosed for a single-chip data processing circuit, such as a smart card. The memory management unit (i) partitions a homogeneous memory device to achieve heterogeneous memory characteristics for various regions of the memory device, and (ii) restricts access of installed applications executing in the microprocessor core to predetermined memory ranges. The memory management unit provides two operating modes for the processing circuit. In a secure kernel mode, the programmer can access all resources of the device including hardware control. In an application mode, the memory management unit translates the virtual memory address used by the software creator into the physical address allocated to the application by the operating system in a secure kernel mode during installation. The memory management unit implements memory address checking using limit registers and translates virtual addresses to an absolute memory address using offset registers. The memory management unit loads limit and offset registers with the appropriate values from an application table to ensure that the executing application only accesses the designated memory locations. The memory management unit can also partition a homogeneous memory device, such as an FERAM memory device, to achieve heterogeneous memory characteristics normally associated with a plurality of memory technologies, such as volatile, non-volatile and program storage (ROM) memory segments. Once partitioned, the memory management unit enforces the appropriate corresponding memory characteristics for each heterogeneous memory type.
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