Sneak Path Free Reconfiguration With Minimized Programming Steps for Via-Switch Crossbar-Based FPGA

摘要

Field programmable gate array (FPGA) that utilizes via-switches, which are a kind of nonvolatile resistive RAMs, for crossbar implementation is attracting attention due to higher integration density and performance. However, programming via-switches arbitrarily in a crossbar is not trivial since a programming current must be provided through signal wires shared by multiple via-switches. Consequently, depending on the previous programming status in sequential programming, unintentional switch programming may occur due to signal detour, which is called the sneak path problem. This article identifies the circuit status that causes the sneak path problem and proposes a sneak path avoidance method that gives sneak path free programming order of via-switches in a crossbar. We prove that sneak path free programming order necessarily exists for arbitrary ON-OFF patterns in a crossbar as long as no loops exist. This article also proposes a partial reconfiguration method that achieves the minimum number of switch programming steps while avoiding the sneak path problem. This method contributes to the extension of via-switch lifetime and fast reconfiguration of the via-switch FPGA. Experimental results show that the proposed partial reconfiguration method reduces the number of programmed switches by 77.4% compared to the conventional approach. This 77.4% reduction improves the number of reconfigurations of the via-switch FPGA by 4.4x and reduces reconfiguration time by 77.4%.