Abstract: The present invention provides for use in a data processor a method for mapping a respective machine language instruction stored by cache storage unit to a respective microprogrammed algorithm stored in control storage unit means, wherein the respective machine language instruction includes an opcode field with a prescribed value and at least one nonopcode field with one of a plurality of values, the method, comprising the steps of in the course of one data processor clock cycle, providing the respective machine language instruction to a decoder for converting the prescribed opcode field and the at least one nonopcode field of the respective machine language instruction into a respective combination of decoded signals which corresponds to the prescribed opcode field value and that at least one nonopcode field value of the respective machine language instruction; and providing the respective combination of decoded signals to combinational logic for converting the respective combination of decode signals into a