Sequential circuit synthesis using input delays

Abstract

This paper describes a new type of circuit realization for asynchronous sequential circuits of the type described by Huffman and Caldwell. This new realization differs from conventional realizations in that delay elements are associated with the input lines. A synthesis procedure is developed for this new type of circuit, and it is proved that a large class of sequential circuits can be realized in this way without including any delay elements in the feedback loops. This class includes sequential circuits containing essential hazards. It is also shown with an example that the resulting circuits can sometimes contain fewer feedback loops and be more economical than conventional circuit realizations.