On designing universal logic blocks and their application to FPGA design

We present a general methodology to determine the logic function of a programmable cell. It is based on the concept of universal logic gate (ULG) that is capable of being configured to a given set of functions. The cells studied here can be configured to the desired functionality by applying input permutation, negation, bridging or constant assignment, or output negation. One application of this technique is to select an appropriate programmable cell structure for FPGA architecture. The Actel 2 and the three-input look-up table cells are studied and compared to the cell that has been designed using the approach described here. Experimental results suggest that the new cell behaves as well as the Actel 2 cell in terms of logic power, but requires substantially less area and wiring overhead.