Aspects of system-on-chip design for FPGAs

Sammanfattning: Due to the increasing NRE costs of recent ASICs, the use of FPGAs is expected to continue to increase. While the first FPGAs were limited devices useful mainly for glue logic, todays FPGAs are highly capable devices used in many different application areas including telecommunication, multimedia, medical, and automotive. This means that many VLSI designers need to deal with FPGAs, either as the primary target, or as a prototype platform. The design methodology for an ASIC and FPGA are similar, but if high performance is expected from the FPGA, it is necessary to take FPGA limitations related to memories, data path components, I/O, and routing delays into account early in the design cycle for both FPGA prototyping and FPGA products.This thesis investigates these limitations through three case studies of important VLSI building blocks. The thesis also discusses how a designer can gain additional information from the FPGA backend flow through custom tools and presents a framework for designing such tools.The first case study discusses the opportunities and problems when designing both the data path and control path components of a high speed processor in an FPGA. The resulting processor core is a RISC processor with some DSP extensions which has a clock frequency which is significantly higher than the Micro blaze processor which has been specifically developed for Xilinx FPGAs. This case study focuses on the tradeoffs which are necessary to reach this performance in an FPGA.The second case study describes how a floating point adder and multiplier can be optimized for FPGAs. This is a very important area as the use of floating point arithmetic can significantly reduce the design time of some applications. The solution presented in the thesis outperforms previous academic publications and has a performance similar to commercial offerings.The third case study presents a packet switched Network-on-Chip (NoC) architecture. While NoCs are not commonly used in FPGA designs today it is expected that they will become an important component in future FPGA designs, especially when prototyping large NoC based ASICs.Finally, a framework is presented which allows a designer to write custom backend tool by modifying Xilinx XDL files. While the framework is already useful for some tasks, the main reason for including it is to inspire both researchers and developers to look into this area by showing that it is actually quite easy to write such tools.