consensus theorem and power

I don't know what you mean by "consensus term", could you elaborate? If you are talking about overlapping logic terms, these don't make much difference for LUT logic, which is guaranteed glitchless for single input transitions.

John

Hi John,

Sorry for the delay in responding. I am not sure about what you mean by overlapping logic terms. By consensus term I mean use of the expression -

ab + a'c = ab + a'c + bc. In this case, bc is the consensus term.

As you probably know, bc prevents any glitches in the output when a changes. So what I am implying is that the switching activity on the output is reduced if we use the bc term.

Thanks.

-sanjay

Sanjay, if you are talking about Look-Up-Table logic, there is no difference between the approaches. In your case of three inputs, abc, you must define the output for all 8 possible input codes in the Table (or call it a ROM). Whether you think of "consensus" has no relevance. LUT logic is a brute-force implementation. You get no glitch on the output when you change one input, (well, you may get a change, but no glitch !) and you also get no glitch when you change two inputs, provided all 4 permutations of these two iputs create the same output (not true in your specific example). Peter Alfke, Xilinx Applications