The need for flexible computational power has motivated many researchers to incorporate run-time reconfigurable logic into their architectures. Most contemporary experiments include commercial FPGA's serving as reconfigurable hardware. Unfortunately, the FPGA does not exhibit the same run-time flexibility as the Instruction Set Processor (ISP) e.g. when it comes to ease and speed of setting up a task. In addition, FPCA 's tend to be less suited than traditional ISP's to accommodate control-flow dominated tasks. Obviously, it is possible to alleviate some of these issues by using a reconfiguration hierarchy (e.g. placing and configuring an ASIP or coarse grain reconfigurable block into the FPCA). This paper illustrates how our operating system transparently manages the complexity of hierarchical reconfiguration. In addition, this paper highlights the benefits and drawbacks of employing multiple hierarchical levels of configuration. As a proof of concept, we developed a filtering application on top of an in-house 16 bit microcontroller and a parameterizable filter block, both instantiated inside an FPGA.
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