METHOD AND APPARATUS FOR MULTI-MODE OPERATION IN A SEMICONDUCTOR CIRCUIT

摘要

A multi-mode architecture is disclosed for a semiconductor circuit, such as a smart card, microcontroller or another single-chip data processing circuit. The disclosed semiconductor circuit supports at least two modes of operation. A memory management unit restricts each application to a predetermined memory range and enforces certain mode-specific restrictions for each memory partition. In a secure kernel mode, all resources and services on the semiconductor circuit, such as special function registers, are accessible. In an application mode, certain special function registers are not accessible (and thus, the resources associated with such special function registers are also not accessible). The operating system is normally executed in a secure kernel mode, where most, if not all resources are accessible. Likewise, a user application is normally executed in a user mode, where certain resources are not accessible. If an application attempts to access a restricted resource in a user mode, a fault interrupt is generated. If a user application needs to access a restricted resource that is only available in the kernel mode, the user application invokes the kernel mode using an interrupt.