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UBC Theses and Dissertations

Technology mapping and layout synthesis of DCVS Wong, Carly


Differential Cascode Voltage Switch (DCVS) logic is a dynamic logic family that has a number of desirable properties. In particular, it is hazard-free, easy to make fully robust path delay-fault testable, and has a number of unique timing properties that make it very suitable for self-timed circuits. This thesis investigates the problem of implementing logic with DCVS, and in particular, the automatic synthesis of DCVS circuits. This task is challenging because DCVS gates are usually significantly more complex than standard static CMOS both in terms of internal connectivity and number of inputs. Most of the work done in circuit synthesis, such as technology mapping and layout synthesis, are not directly applicable to DCVS. We present DMAP, a technology mapping and layout synthesis system for DCVS. The system operates in three steps. First, the combinational circuit is decomposed and partitioned into sizable Boolean function clusters. Secondly, DMAP takes each cluster function, and generates a DCVS cell layout that implements that function. We develop a heuristic algorithm for finding a suitable transistor path to lay out the DCVS pull-down network. Finally, the generated DCVS cells are placed and routed inside the CADENCE environment. Experimental results indicate that DCVS circuits can be implemented with considerably fewer cells than by conventional mapping techniques. Furthermore, the number of nets that need to be wired is typically less than twice the number of nets used in standard mapping. This is better than the intuitive assumption that dual-rail circuits require twice as many wires as their single-rail counterparts. Large DCVS circuits can be feasibly produced. DMAP is a first step towards an integrated system for dynamic circuit synthesis.

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