Ouch! Problem 5b

Ooops!  It looks like I must have disengaged my brain before I wrote this
email.  It turns out you do need to be able to add extra inputs to the box,
where each such input is a constant (that is, always 0 or always 1).  BUT,
again, no additional logic gates, just the two 2-to-1 muxes.

Sorry.  Good luck!

Yale Patt

On Fri, Sep 22, 2017 at 09:17:28PM -0500, Yale N. Patt wrote:

> It seems like I can not walk from one point to another on the campus without
> one of my 306 students stopping me with another creative mechanism to add to
> the statement of Problem 5B. I do admire the creativity to try to get around
> the difficulty of the problem, but the challenge is to solve the problem
> (which I admit is very tricky and only there to provide a challenge for those
> who like challenges) as stated.
>
> Let me try one more time to make it clear.
>
> 1. Draw a box.
> 2. Label two inputs to the box A and B.
> 3. Label the output of the box F
>
> You have two 2-to-1 muxes to use as you see fit. Each mux has four
> terminals: three inputs (source 1, source 2, select line) and one output
> (the output of the mux).
>
> Your job: Put the two muxes in the box and make whatever connections you need
> to so that the output F = A XOR B. Connections are to inputs A,B, to the
> output F, and to the four terminals of each of the muxes.
>
> You are not allowed to add NOT gates, you are not allowed to add additional
> input 0's or input 1's. You are not allowed to anything other than wires
> to make the connections you need inside the box.
>
> To stop the obsessing about 5B, we will not deduct any points from your
> problem set if you do not solve problem 5B.
>
> Have fun!
>
> Yale Patt
>