Technology mapping of heterogeneous LUT-based FPGAs

New techniques have been developed for the technology mapping of FPGAs containing more than one size of look-up table. The Xil inx 4000 series is one such family of devices. These have a very large share of the FPGA market, and yet the associated technology mapping problem has hardly been addressed in the literature. Our method extends the standard techniques of functional decomposition and network covering. For the decomposition, we have extended the conventional binpacking (cube-packing) algorithms so that it produces two sizes of bins. We have also enhanced it to explore several packing possibilities, and include cube division and cascading of nodes. The covering step is based on the concept of flow networks and cut-computation. We devised a theory that reduces the flow network sizes so that a dynamic programming approach can be used to compute the feasible cuts in the network. An iterative selection algorithm can then be used to compute the set cover of the network. Experimental results show good performances for the Xilinx 4K devices (about 25% improvement over MOFL and 10% over comparable algorithms in SIS in terms of CLBs).

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