I'm supposed to realize the logic of a truth table (attached) with a multiplexer.

Using the method in my text book I developed the connections below. My MUX has 3 data selectors (D, C and B) and 8 data inputs (0-7).

Input Connected to
0 High
1 A
2 High
3 A
4 Low
5 A
6 not A
7 High

I went through the states and it seems to produce the same output as the truth table.

But in the solution (attached), my teacher did it differently, in a way that doesn't make sense to me. Can someone explain?

 

You are using D, C, and B as the select lines to the mux and your teacher is using A, B, and C, with C as LSB. These will yield totally different logic on the front end, so your result may be completely correct as well.

From the table, when ABC is 000 and D is 0 the output is 1. When ABC is 000 and D is 1 the output is 0. Therefore, you teacher put the first output as 'not D.'

 

I read recently a nice formula to calculate your MUX inputs.

Let F(A,B,C,D) be your boolean function and ABC (from MSB to LSB) your select inputs.

Ii=F(Ai,Bi,Ci,D), where Ai, Bi and Ci are the nescessary inputs to achieve the selection of the number i.

i.e. on your truth table, input 000 is I0=F(0,0,0,D)=D'.