A high-speed and low-voltage associative co-processor with exact Hamming/Manhattan-distance estimation using word-parallel and hierarchical search architecture

We present a new concept and its circuit implementation for a high-speed and low-voltage associative co-processor with Hamming distance ordering. A hierarchical search architec-ture keeps high speed in large input number. Our circuit im-plementation allows unlimited data base capacity and achieves low-voltage operation under 1.0V for SoC applications, which are difficult for the conventional analog approaches. The search logic embedded in a memory cell realizes word-parallel Ham-ming distance ordering for high-speed sorting/routing appli-cations as well as near/nearest-match detection for recogni-tion. Our fabricated 0.18 µm 64-bit 32-word associative co-processor operates 411.5 MHz and 40.0 MHz at 1.8V and 0.75V respectively