Patent US 4,179,731

A microprogrammed control system comprises: a memory for storing a microprogram programmed with microinstructions; a memory for storing microinstructions for branching microinstruction; an address register for storing the address of the microinstruction to be next executed; and a microinstruction register for storing the microinstruction to be executed. The program operation of the microprogrammed control system depends on whether the micro-instruction stored in the microinstruction register is the branching one or not. In the case of non-branching microinstruction, the operation of ordinary microinstructions is executed. In the case of branching microinstruction, a special operation is executed for making the operation of the branching microinstruction equivalent to that of the ordinary microinstruction.