UPGRADEABLE HIGHLY INTEGRATED EMBEDDED CPU SYSTEM

A system and method in accordance with the present invention provides for an embedded CPU system which is upgradeable through the use of an external CPU which can be utilized therewith. In a first aspect, the embedded CPU system includes a CPU and a plurality of devices which are accessible by the CPU, via a device control register bus. The embedded CPU system includes logic coupled to the device control register bus for allowing access to the devices within the embedded CPU system by an external CPU. In a preferred embodiment the present invention provides a highly integrated set top box controller with a processor performance that services the low-end with the added advantage of additional performance with the EMCPU operating as an I/O assist processor to the EXCPU. When the EXCPU operates as the primary processor these two processors serve as a high end set top box controller. A system and method in accordance with the present invention can also preserve much of the software programming model when migrating from a low end processor set top box controller to a higher end solution. A system and method in accordance with the present invention also offers a choice of preserving much of the existing software investment by allowing different processor architectures to function as the EXCPU.