CHAPTER 7

Verification of Modular Asynchronous Circuits

7.1 ABOUT ASYNCHRONOUS CIRCUITS

Asynchronous circuits are sequential circuits that operate without any global clock control. In an asynchronous circuit each component starts its computation as soon as all the required data are available and transmits its outputs to the next components as soon as its computation is completed. In synchronous (clock-controlled) circuits the transfer of data is delayed until the occurrence of the next clock signal. Thus an asynchronous circuit may, in principle, be faster than its synchronous counterpart. Furthermore, the asynchronous approach assists in reducing power consumption. Therefore asynchronous circuits are of particular interest in connection with portable devices and airborne systems.

However, it turns out that synchronous circuits are easier to design than asynchronous ones. In recent years there has been a great surge of interest in asynchronous designs, in view of the above advantages. Both the practical and the theoretical aspects of such designs are being extensively investigated. For more details, see Reference 1.

7.1.1 Modular Asynchronous Circuits

In this text we are particularly interested in modular asynchronous circuits, which are designed as a composition of basic modules. Such modules are more complex than simple gates; their correct behavior is to be assured by suitable circuit design rather than by logic design. A special class of such circuits is formed by delay-insensitive ...

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