
The entire thing is based off of this image, so all credit to them. Uses XOR, AND, & OR gates for the entire thing.
Take 2 4-bit arrays and then feed them in in the following order:
LEDs from Sum 0-3 for display. Switches from A0-3 and B0-3.
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | in0 | out0 | |
| 1 | in1 | out1 | |
| 2 | in2 | out2 | |
| 3 | in3 | out3 | |
| 4 | in4 | out4 | |
| 5 | in5 | ||
| 6 | in6 | ||
| 7 | in7 |