# Homework Help: Implementing a 3 to 8 Binary Decoder.

1. Oct 23, 2013

### shamieh

Show how the function f(w1,w2,w3,) = Ʃm(0,1,2,4,7) can be implemented using a 3 to 8 binary decoder and an OR gate (hint look at a MUX built using a decoder and figure out how to remove the AND gates.

I know that a 3 to 8 decoder would have something like this:
1. w1 w2 w3 f0 f1 f2 f3 f4 f5 f6 f7
2. 0 0 0 1 0 0 0 0 0 0 0
3. 0 0 0 0 1 0 0 0 0 0 0
4. 0 1 1 0 0 1 0 0 0 0 0
5. 0 1 0 0 0 0 1 0 0 0 0
6. 1 0 1 0 0 0 0 1 0 0 0
7. 1 0 0 0 0 0 0 0 1 0 0
8. 1 1 1 0 0 0 0 0 0 1 0
9. 1 1 0 0 0 0 0 0 0 0 1

The problem I'm running into is this: There are NO good examples of MUX online, there are also NO good examples really of how to do this when given Ʃm(some numbers in here) If you don't believe me, just try to google it. I also know that this circuit is like w1,w2,w3, connected to a inverter then connected to a and gate.

Thanks for your time.

2. Oct 23, 2013

### shamieh

I actually just figured this one out you connect the three inputs to a multiplxer and then connect all the ones that output a 1 to a or gate.