Speedup of Self-Timed Digital Systems using Early Completion

Scott C. Smith, Missouri University of Science and Technology

This document has been relocated to http://scholarsmine.mst.edu/ele_comeng_facwork/1888

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An Early Completion technique is developed to significantly increase the throughput of NULL Convention self-timed digital systems without impacting latency or compromising their self-timed nature. Early Completion performs the completion detection for registration stage i at the input of the register, instead of at the output of the register as in standard NULL Convention Logic. This method requires that the single-rail completion signal from registration stage i+1 , Ko i+1 , be used as an additional input to the completion detection circuitry for registration stage i , to maintain self-timed operation. However, Early Completion does necessitate an assumption of equipotential regions, introducing a few easily satisfiable timing assumptions, thus making the design potentially more delay-sensitive. To illustrate the technique, Early Completion is applied to a case study of an optimally pipelined 4-bit by 4-bit unsigned multiplier utilizing full-word completion, where a speedup of 1.21 is achieved while self-timed operation is maintained and latency remains unchanged.