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A New Logic Synthesis, ExorBDS. Kelsey Muma Department of Electrical Engineering, University of Saskatchewan Seok-Bum Ko Department of Electrical Engineering, University of Saskatchewan. A New Logic Synthesis, ExorBDS. Outline Introduction Background ExorBDS
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A New Logic Synthesis, ExorBDS • Kelsey Muma Department of Electrical Engineering, University of Saskatchewan • Seok-Bum Ko Department of Electrical Engineering, University of Saskatchewan ExorBDS
A New Logic Synthesis, ExorBDS • Outline • Introduction • Background • ExorBDS • Experimental Method and Results • Conclusions ExorBDS
Introduction • FPGAs • Useful for rapid prototyping • Excellent re-programmability features • Higher cost/logic than ASICs • Cannot be as efficient when also trying to be programmable ExorBDS
Introduction • Commercial EDA tools provide technology-independent minimization, followed by technology-dependent mapping • We believe current EDA tools sub-optimal, particularly for XOR-intensive functions (maybe others as well) ExorBDS
Background • Parity Prediction Circuits • Basic error checking method • Prediction circuit involves XORing all outputs to determine expected parity bit ExorBDS
Background • Overview of Xilinx Virtex II Pro • Experimental results based on this FPGA (XC2VP2) • Contains CLBs • Each CLB contains 4 slices • Each slice contains 2 4-input LUT • 4-LUT: used for comparing methods ExorBDS
ESOP-minimization • Often requires fewer product terms/literals than traditional SOP minimization • FPGA logic resource usage based on number of inputs, not on Boolean complexity (as in ASICS) ExorBDS
BDD-based Decomposition • BDS • BDD-based program which decomposes circuits using BDDs as basic data structure • Decomposing allows removal of shared nodes, as well as better mapping to FPGA LUT (Decompose circuit, so functions can be grouped into k-input functions) ExorBDS
ExorBDS • Includes single stage of ESOP-minimization, followed by a stage of BDD-based decomposition 1. Use Exorcism4 for ESOP-minimization 2. Use BDS for BDD-decomposition ExorBDS
ExorBDS Parity prediction circuit Exorcism4 BDS Convert to VHDL, synthesize ExorBDS
Experimental Methods • Synthesized parity prediction functions of 14 MCNC benchmark circuits using 4 methods: • Direct Method (Using commercial EDA tools only) • Exorcism4 • BDS • ExorBDS ExorBDS
Experimental Results • Results compared based on following metrics: • Area (4-LUT) • Delay (max. combinational path delay) • Area-Delay Product ExorBDS
Experimental Results* *: misex3 excluded ExorBDS
Conclusions • These results would allow FPGA designer to have much more logic than the same FPGA using commercial tools • Could help bridge the cost/logic gap between FPGA and ASIC ExorBDS
Future Work • It is believed such efficiencies can also be extended to arithmetic circuits and error correcting/detecting circuits • Analysis of ExorBDS on NON XOR-intensive circuits • If results are as good or better, ExorBDS will provide a general solution to synthesis ExorBDS
Questions ? ExorBDS