How Do You Build a Circuit Using a 4:1 Multiplexer?

[transgalactic]

build the circuit of
http://img517.imageshack.us/my.php?image=img86381xv6.jpg

using 4:1 multiplexer

i don't know what the plus meens
i know that the second after the plus is the don't care group
but i don't know how to solve it

i wrote a unified truth table for both groups
http://img187.imageshack.us/my.php?image=img86411ml5.jpg

how do i build a circuit??

 

[berkeman]

Hmm, that's a challenging one. I think you've done the correct job of making the K-map, and now you need to play with different combinations of what to make the don't-cares, and what you can do with a 4:1 multiplexer. Your 4:1 MUX actually has 6 inputs and 1 output, right? There's the 4 inputs to the MUX, plus the 2 selector lines. So look at some variations of the truth table with different configurations of the X values (don't cares), and see if the simplest truth table variations are amenable to using a 4:1 MUX to form the outputs of the truth table. I haven't solved the problem myself yet, but that's how I would approach it.