A coprocessing core is provided with a unique architecture wherein the register block of the coprocessor is divided into a plurality of sub-blocks containing registers. In indirect addressing of the register block, the value loaded into a base pointer points to a particular one of the plurality of sub-blocks and activates the registers therein for read-write access. Changing of the base pointer value using only a single instruction brings another set of registers in a sub-block into activation. Unless relatively accessed, read only access is available to the registers in the register block. This architecture advantageously facilitates single instruction context switching, non-stacked machine operation and low latency interrupt handling. The architecture, as well as the programmability of the coprocessing core, further facilitates use of the device in a universal input/output controller application for connection between a host processor and plurality of different types and kinds of peripheral devices.