Synthesis of speed-independent circuits from signal transition graphs

• Main Authors: Lin,Kuan-Jen, 林寬仁
• Other Authors: Lin,Chen-Shang
• Format: Others
• Language: en_US
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/73868084652037802660

博士 === 國立臺灣大學 === 電機工程學研究所 === 84 === Asynchronous design has received the resurgence of interest and been expected to become an important alternative to synchronous design. In this thesis, we presents an automatic synthesis sys- tem which adopts the Signal Transition Graphs (STGs) as input specifications and results in hazard-free asynchronous circuits. Our synthesized circuits from STGs are speed independent, which can operate correctly regardless of variations in delays of elementary gates. To realize such circuits, we firstly propose a realization circuit model based on a practical configuration and prove that a signal implemented with this circuit model is speed-independent.Then, we propose a novel graph transformation, Characteristic Graph (CG), to encapsulate all feasible solutions of the original STG in reduced size, which compares favorably to the state graph. Based on the CG, we can verify the hazard-freeness of circuits and explore the exact optimization of circuit realization without restoring to the state graph. We will propose a necessary and sufficient condition for an STG to have hazard-free implementation, which has not yet been reported. Furthermore, we will formulate the problems of exact-optimization as well-known graph problems and proved their complexities to be NP-hard. A heuristic method is thus proposed and evaluated with examples from $sis$ and a set of STGs with thousands of states. We obtain significant improvement over previous works in CPU time.