# Implement function with 4:1 & 2:1 Multiplexers

Discussion in 'Homework Help' started by tquiva, Nov 13, 2010.

1. ### tquiva Thread Starter Member

Oct 19, 2010
176
1
I'm trying to implement four functions using a minimum number of 2:1 and 4:1 muxes with NO additional gates.

This is my truth table:

Right now, I'm currently working on function Z.
I grouped the rows into pairs accordingly:

When ABC=000, Z = D
When ABC=001, Z = D
When ABC=010, Z = D
When ABC=011, Z = D

When ABC=100, Z = D'
When ABC=101, Z = D'
When ABC=110, Z = D'
When ABC=111, Z = D'

So therefore I would need a mux with 8 data inputs?
I put two 4:1 muxes together, with the select inputs labeled with A, B, C
And I just labeled the data inputs by D.H (high), or D.L (low) according to the pairs above

This is what I have so far for function Z.
I really don't know how to label the pins or make the connections to connect both muxes together. Could someone please help me on this?

Edit:
I edited the above circuit to this one. But I still don't know how to cascade several muxes. I don't know where to connect the select inputs and other connections. Could someone please help me asap?

Last edited: Nov 13, 2010
2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Connect B and C inputs to S1 and S0 of both multiplexers respectively. Use A input to select which multiplexer is active. When A=0, the top multiplexer shall be active (connect to A via NOT gate) and when A=1 the bottom multiplexer shall be active (connect directly to A). However, you don't need these multiplexers to achieve that. Z=D when A=0 and Z=D' when A=1, thus a simple logic circuit can achieve this.

tquiva likes this.

Oct 19, 2010
176
1
thank you!