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VLSI Design
Volume 15 (2002), Issue 3, Pages 629-635

Improving the Timing of Extended Finite State Machines Via Catalyst

Electrical Engineering Department, National Tsing-Hua University, HsinChu, Taiwan

Received 15 March 2001; Revised 30 January 2002

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We propose a timing optimization technique for a complex finite state machine that consists of not only random logic but also data operators. In such a design, the timing critical path often forms a cycle and thus cannot be cut down easily by popular techniques such as pipelining or retiming. The proposed technique, based on the concept of catalyst, adds a functionally redundant block—which includes a piece of combinational logic and several other registers—to the circuits under consideration so that the timing critical paths are divided into stages. During this transformation, the circuit's functionality is not affected, while the speed is improved significantly. This technique has been successfully applied to an industrial application—a Built-In Self-Test (BIST) circuit for static random access memories (SRAMs). The synthesis result indicates a 47% clock cycle time reduction.