Decomposition-Based Vectorless Toggle Rate Computation for FPGA Circuits

Abstract

This paper presents a novel and accurate method of estimating the toggle rates of signals in field-programmable gate array (FPGA)-based logic circuits without the use of simulation vectors. Compared to previous vectorless techniques, our approach provides improved accuracy-of-results, especially for individual signals, which could be leveraged by computer-aided design (CAD) tools for performing power optimization of logic circuits. Increased accuracy is achieved by using stochastic methods that estimate the transition densities at FPGA logic elements while accounting for both spatial and temporal correlation of logic signals. Spatial correlation is calculated by leveraging a unique XOR-based decomposition technique that provides both accurate results and fast computation times. We also consider the delay information of implemented circuits, providing for a comprehensive treatment of glitches, including the effects of inertial limits on power dissipation. Our toggle-rate estimation approach has been tested on a commonly used set of Microelectronic Center of North Carolina circuits, as well as a set of industrial circuits targeted to Altera Stratix II FPGAs. Results show that our techniques provide a three times lower percent error, while maintaining a low processing time, when compared to two existing techniques: the vectorless estimation tool shipped with the commercial Quartus II 8.0 CAD tool, and the ACE v2.0 academic tool produced from the University of British Columbia, Vancouver, BC, Canada.