On designing ULM-based FPGA logic modules
Shashidhar Thakur, Martin D. F. Wong · 1995
FPGA technologies employ replicated programmable logic blocks. These can be look-up tables or more complex macro-cells. In this paper, we give a method to design macro-cell logic modules, based on an extension of classical work on designing Universal Logic Modules (ULM ). Specifically, we give a technique to design a class of logic modules that specialize to a large number of functions under complementations and permutations of inputs, bridging of inputs and assignment of 0/1 to inputs. Thus, a lot of functions can be implemented using a single logic module. The significance of our work lies in our ability to generate a large set of such logic modules. A choice can be made from this set based on design criteria. We demonstrate the technique by generating a set of 471 8-input functions that have a much higher coverage than the 8-input cells employed by Actel's FPGAs. Our functions can specialize to up to 23 times the number of functions that Actel functions can. We also show t...