Microprocessor implemented data processing system capable of emulating execution of special instructions not within the established microprocessor instruction set by switching access from a main store portion of a memory

摘要

A microprocessor chip which is capable of executing a specific subset of instructions on behalf of the main storage portion of a computer memory can be made to emulate direct execution instructions not in that specific subset while working on behalf a control storage portion of the computer memory in a manner which is transparent to the main storage portion by means of a novel set of operand space selection instructions in the control storage portion and a novel switching circuit on the microprocessor chip which controls the access of the chip to the control store portion and the main store portion.