On the Design of LPM Address Generators Using Multiple LUT Cascades on FPGAs
NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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We propose the multiple LUT cascade as a means to configure an n-input LPM Longest Prefix Match address generator commonly used in routers to determine the output port given an address. The LPM address generator accepts n-bit addresses which it matches against k stored prefixes. We implement our design on a Xilinx Spartan-3 FPGA for n 32 and k 504 tilde 511. Also, we compare our design to a Xilinx proprietary TCAM ternary content-addressable memory design and to another design we propose as a likely solution to this problem. Our best multiple LUT cascade implementation has 5.17 times more throughput, 40.71 times more throughputarea and is 2.97 times more efficient in terms of area-delay product than Xilinx s proprietary design, but its area is only 15 of Xilinx s design. Furthermore, we derive a method to determine the optimum configuration of the multiple LUT cascade on an FPGA.
- Electrical and Electronic Equipment
- Electric Power Production and Distribution