Logic Design using Multiplexers.

[Fraser_Integration]

Hi Forum.

I have the following homework question. Implement the function:

f(A,B,C,D,E) = sigma (0,2,4,6,10,12,13,16,20,26,28,31) with dont care 8,18,27 using two 8to1 line multiplexers and one 2to1line multiplexer using B as the data variable. I did this fine, see the attached .

It then asks "how might you take advantage of the don't care conditions to solve this function using four 4to1line multiplexers"

This has got me baffled. I don't really know where to start, any ideas?

[MilK]

dont care means can be 1 or 0. take dont care = 1 if it simply your result

[Fraser_Integration]

Hi. Thanks for the reply

I understand that with Don't Care conditions you can use an alternative to the B or B' data value, as you will see I put both in the data value column in my attachment where a don't care occurs (green highlighting).

It's more the physical implementation of the four multiplexers, what plugs into what etc.

[Fraser_Integration]

I think I have a solution, I noticed that whenever C = 0, and E = 1 the output was zero, so I just had 3 multiplexers of A'D' to AD and one multiplexer of C'E' to CE with the C'E pin set to zero and the other free fed back into the output of the AD mux's. Sound about right?