HIGH-SPEED MICROPROGRAM CONTROL APPARATUS WITH DECREASED CONTROL STOORAGE REQUIREMENTS

A microprogrammed control apparatus includes a first control store for providing a first sequence of microinstructions and a second control store which includes first and second control store portions providing first and second sets, respectively, of microinstructions. A selection circuit selects a first microinstruction from the first control store followed by a first set of subsequent microinstructions from the second control store portion, etc. A second selection circuit will select either the selected microinstruction from the first selection circuit or control information provided from a control store. The address for reading out the microinstructions from the first and second control store portions is determined in accordance with the branch address field of the microinstruction currently being executed.