SPECIFICATION AND REALISATION OF LOGIC CONTROL PROCEDURES ON THE BASIS OF PRESCRIBED INPUT-OUTPUT CHANGES

Abstract

In this report, a method is outlined for handling the logic control procedures both in the specification level and on the hardware implementation level of the design. The heuristic and intuitive character of constructing the flow chart and defining the states has been reduced to a large extent. This method may result in several kinds of uniform hardware structures for either synchronous or asynchronous control units initially specified only by input-output sequences. Introducing differential mappings for the description of sequential operation, the prescribed sequences for input and output changes can be considered as the initial specification of a control unit. This specification yields a so-called B : K table and aB: K graph as representation of the required operation. The definition of the states is made by interpreting the compatibility relation between the prescribed output changes. . The procedure of the state definition results in the B: K : A set or graph which corresponds to the minimised flow table obtained from the state reduction of incompletely specified sequential circuits. The properties of the canonical B : K set and graph always ensure the existence of an optimal cover. If the fixed hardware structure contains flip-flops for storing the output combination, then the influence of these flip-flops on the state reduction are automatically taken into consideration by the method outlined in the report. Also, by the introduction of an optimal cover for the identifying functions related to the output changes, the logical expressions for the realisation of the hardware can be simplified. The specification and description method, outlined in this report, has the advantage of defining the prescribed sequences of input and output changes in separate fragments. Applying the prescribed input section changes. these separate fragments can be joined together and the B : K set can be calculated systematically. In this way, the specification for the synthesis procedure may become more rigorous than it was initially. However, it is not necessary to form a coherent specification by intuition.