and (2003) The synthesis of cyclic combinational circuits. In: 40th Design Automation Conference. Association for Computing Machinery , New York, pp. 163-168. ISBN 1-58113-688-9 .
If we look closely we see that in the case of combinational logic we had "=" for assignment, and for the sequential block we had "
A general model of a FSM consists of both the combinational Logic and sequentialcomponents such as state registers, which record the states of circuitand are updated synchronously on the rising edge of the clock signal.
Digital circuits are called combinational if they are memoryless: they have outputs that depend only on the current values of the inputs. Combinational circuits are generally thought of as acyclic (i.e., feed-forward) structures. And yet, cyclic circuits can be combinational. Cycles sometimes occur in designs synthesized from high-level descriptions. Feedback in such cases is carefully contrived, typically occurring when functional units axe connected in a cyclic topology. Although the premise of cycles in combinational circuits has been accepted, and analysis techniques have been proposed, no one has attempted the synthesis of circuits with feedback at the logic level. We propose a general methodology for the synthesis of multilevel combinational circuits with cyclic topologies. Our approach is to introduce feedback in the substitution / minimization phase, optimizing a multilevel network description for area. In trials with benchmark circuits, many were optimized significantly, with improvements of up to 30% in the area. We argue the case for radically rethinking the concept of "combinational" in circuit design: we should no longer think of combinational logic as acyclic in theory or in practice, since nearly all combinational circuits are best designed with cycles.
The most common way to model any logic is to use either assign statements or always blocks. An assign statement can be used for modeling only combinational logic and always can be used for modeling both combinational and sequential logic.
The approach seems to reduce the amount of computer resources required to design combinational logic circuits, when compared to our previous research in this area.
From what we have learnt in digital design, we know that there could be only two types of digital circuits. One is combinational circuits and the second is sequential circuits. There are very few rules that need to be followed to get good synthesis output and avoid surprises.
Introduction The problem of interest to us consists of designing a combinational circuit that performs a desired function (specified by a truth table), given a certain specified...
In this paper we propose an approach based on a genetic algorithm (GA) to design combinational logic circuits in which the objective is to minimize their total number of gates.