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Feasibility study for dynamic context switching inpartially reconfigurable FPGAS

Yılmaz, Esat
Reconfiguration of computing and control circuits according to dynamically changing needs is a supportive concept which saves design-time and the space needed for floorplanning in comparison to application specific integrated circuits (ASIC). FPGAs which are commonly used reconfigurable devices have both full and partial reconfiguration features. Dynamic partial reconfiguration is a technique which enables some part of the circuit to be reconfigured while other parts are running. This feature allows the user to switch between different and successive tasks working in a particular block of an FPGA device. Preemption of a task might also be needed in dynamically running circuits for real-time/time-critical application requirements. Preemption requires that all current state information of the circuit is saved somewhere else before running another circuit and to run the previously saved circuit where it was stopped from. This thesis study investigates the feasibility of dynamic context switching in modernday FPGAs. For this, a reconfigurable System-on-Chip (SoC) architecture is examined. Xilinx Zynq SoC is used and AXI4-based partially reconfigurable block structure is implemented. By using DMA, readback and reconfiguration structures are implemented. DDR memory is used to store bitstream files when a partial bitstream file is downloaded to the FPGA. The resulting system designed helps to reduce required resources for big size circuits by providing and enabling a context-save and context-restore mechanism for time-critical tasks with considerably low overhead.