DESIGN OF MICROPROGRAMMED CONTROL UNITS USING SEPARATE MICROPROGRAM FIELDS ENABLED BY STATES

Abstract

In this report a method is outlined for the realisation of high-speed micro programmed control units. The processor is derived from the synchronous phase register structure. The organisation of the micoprogram storage is determined by the states (phases). It means that a separate field of the microprogram storage belongs to each state. In this way, the exponential growth of the number of the necessary memory units can be reduced significantly. This advantage is derived mainly from the separate handling of the storage fields, because each field mutually corresponds to one state, in which only a subset of the input and output signals is affected. The elements of these subsets are determined by the design procedure of the control unit. Thus, the minimization of the Boolean functions, defining the combinational part of the control unit, and the state reduction can be utilized in the simplification of a micro programmed realisation. In the paper, the minimal forms of the Boolean functions and the minimal number of states (phases) are assumed; the influence of the separate micoprogram storage fields on the number of the necessary memory units is examined; a rule is given for constructing the microprograms.