# Implementing functions with multiplexers

Discussion in 'Homework Help' started by dre, Dec 17, 2009.

1. ### dre Thread Starter New Member

Dec 17, 2009
4
0
I'm trying to understand a slide from my notes. I do understand what we're trying to do but not why we are doing it. Basically why are we expanding F so that each term has a B? After the "now compare with:" line where did we get that equation from? Also why are we setting the I0 to 1, the I1 to 0 and the I2 and I3 to C?

Could someone please explain this:

Thanks for any help.

Last edited: Dec 17, 2009
2. ### beenthere Retired Moderator

Apr 20, 2004
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3. ### dre Thread Starter New Member

Dec 17, 2009
4
0
Thanks for the heads up.

Dec 17, 2009
4
0

5. ### Ratch New Member

Mar 20, 2007
1,068
4
dre,

Download the attached file. First thing we do is get all the minterms of the desired function. In your case they are 0,1,5,7

Then we make an implementation table. I made two of them. The first shows you how to connect the A variable to the inputs of the mux. You insist on connecting the C variable to the inputs, so I did a second one for that too. The inplementation table is filled in with the two of the variables assigned to s0 and s1 of the mux. Next the top row is assigned X', which represents the third variable. The bottom row is assigned X. Next each minterm is circled in the implementation table. If only the top state is circled in the column, then the X' term is connected to the Ix input of the mux. If only the bottom state of the column is circled, then the X term is connected to the Ix input of the mux. If both the top row and bottom row of the column are circled, then a 1 is applied to Ix. If the column has no circles, then a zero is applied to Ix.

Ratch

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