Circuit design

Abstract

In the fourth chapter questions of analysis and synthesis of asynchronous sequential circuits are examined. In this connection a group of trigger-type devices is allocated. In general case they are represented by a certain venjunctive function of two variables. This function obeys the rules of operation of a bistable cell in its definitely restricted mode. To thoroughly characterize trigger devices a new concept is introduced in the form of memory formula, which is used alongside with setting operations. Also behavioral model of circuits with memory is developed. It is a zone model, basic configurations of which compose all possible transitions between setting zones and memory zone. Mathematical apparatus of venjunction is used for analysis of positive and negative feedbacks. Some ways are proposed for interruption of spurious oscillations and for retention of settings which are caused by short-pulse signals. Function of sequention is realized by a digital device, named sequentor. The corresponding logical circuits are developed. They are represented in three forms according to the method used for decomposition of sequention. Sequentor contains venjunctors, which in turn are based on bistable cells. Such structure allows constructing regular models for sequential circuit design. The corresponding procedures are proposed for synthesis of asynchronous digital devices. Available structural features are demonstrated by an example. © 2011 Springer-Verlag Berlin Heidelberg.