HW Solution Errors

[vbanuelo]

I was looking through the HW 1 solutions. And it looks like the very last one has an error.

The problem was 5b and it was implementing (xy!z + z + !x!y + xy) using only nor gates.

The answer given was
!( !(!x+!y+z) + z + !(x+y) + !(!x+!y) )

This is the logic for !(xy!z + z + !x!y + xy) since only a single inversion was added.

It should instead be !( !( !(!x+!y+z) + z + !(x+y) + !(!x+!y) )). Since !!A = A.

and the picture should have another nor gate attached to the final output.


Maybe people could add this thread when they find other hw solution errors.

[vbanuelo]

The book states that there is a 1 for whenever there is exactly 2 or exactly 3 positive variables.

So the correct table is

\WX
YZ\ 00 01 11 10
00 | 0 | 0 | 1 | 0 |
01 | 0 | 1 | 1 | 1 |
11 | 1 | 1 | 0 | 1 |
10 | 0 | 1 | 1 | 1 |

My correct answer was a POS of (X + Y + Z) (W + Y + Z) ( W + X + Y) ( W + X + Z)
16 inputs + 5 gates for a cost of 21.

[mrg]

Thanks for the fixes Victor. I think that some of these I noticed/was informed after I posted the solutions and I did not fix the solutions.