A Novel Characterization Method of Click Element Based on Cutting Feedback Loops in Standard Cell Library Design

Click element is frequently used in asynchronous circuits. However, we have to use netlist to instantiate it and the output pulse width will change according to the placement and routing every time when we synthesis it. To address the problem, we design a standard cell library for Click element. However, it is difficult to characterize the Click element with commercial EDA tools for the indescribable function of its output pins in the feedback structure. In this paper, we propose a novel method to characterize Click element by cutting the feedback loops when building up the library and reconnecting the cut points when describing it with Verilog. As a result, the function of output pins could be described during characterization and the function of Click is maintained. The method has been verified by the simulation after placement and routing. The comparison between the Click instantiated by netlist and the full-custom standard cell of Click shows that the latter has 20.8% less area and 63.7% less power consumption than those of the former.