An Improved Overlay and Mapping Algorithm Supporting Rapid Triggering for FPGA Debug

Abstract

Embedded system designers can benefit from FPGA accelerators to achieve higher performance and efficiency. However, there are challenges that do not exist in software development; using software simulators to validate large and complex hardware designs can be extremely slow and impractical. Debugging designs implemented on an FPGA enables running the design at speed for long runs and more exhaustive test cases. However, limited observability is the primary challenge in hardware debug. To enhance hardware observability, trace-buffers and a trigger circuitry are inserted into the design. During the device operation, a history of signals of interest is recorded into the trace-buffers for off-line debug and validation. Recompiling the design every time the designer wishes to modify the trigger condition results in long debug turn-around times and reduced productivity. In this work, we present a pre-synthesized overlay fabric and algorithm to enable rapid triggering; during debug turn-around, TriggerPlus , a greedy algorithm, is used to implement a trigger circuit on the overlay. TriggerPlus is fast and simple, yet still capable of mapping the trigger circuit to the overlay fabric. We evaluate our techniques using VPR, showing that using our overlay and mapping algorithm together is at least an order of magnitude faster than the previous work resulting in a significant reduction in debug turn-around times.