Low-power FSMs in FPGA: Encoding alternatives

Abstract

The final publication is available at Springer via http://dx.doi.org/10.1007/3-540-45716-X_36Proceedings of 12th International Workshop, PATMOS 2002 Seville, Spain, September 11–13, 2002In this paper, the problem of state encoding of FPGA-based synchronous finite state machines (FSMs) for low-power is addressed. Four codification schemes have been studied: First, the usual binary encoding and the One-Hot approach suggested by the FPGA vendor; then, a code that minimizes the output logic; finally, the so-called Two-Hot code strategy. FSMs of the MCNC and PREP benchmark suites have been analyzed. Main results show that binary state encoding fit well with small machines (up to 8 states), meanwhile One-Hot is better for large FSMs (over 16 states). A power saving of up to the 57% can be achieved selecting the appropriate encoding. An areapower correlation has been observed in spite of the circuit or encoding scheme. Thus, FSMs that make use of fewer resources are good candidates to consume less power.Ministry of Science of Spain, under Contract TIC2001-2688-C03-03, has supported this work. Additional funds have been obtained from Projects 658001 and 658004 of the Fundación General de la Universidad Autónoma de Madrid