MICROPROGRAM CONTROL SYSTEM

According to the present invention, in a data processing unit which executes pipeline processings by developing an instruction into multiple flows through microprogram control, is a method provided where the microinstruction is divided into a part for controlling a first stage of pipeline and a part for controlling second and successive stages. The part for controlling the first stage is read simultaneously with the part for controlling the second and successive stages of the flow prior to the current flow. The present invention thus provides an advantage in that microprogram control can be employed for the first stage of the pipeline and resulting in a data processing unit which is capable of executing more flexible pipeline processings than the prior art can be formed. In an instructs a field for controlling the first stage of pipeline is separated from the fields for controlling the other stages and it is read at the same timing as that for reading the fields for controlling the second and successive stages of the flow just prior to the current flow. As a result, the first state of pipeline in the second and successive flow is controlled by microprogram control.