| in | sel | a | b | c | d |
| 0 | 00 | 0 | 0 | 0 | 0 |
| 0 | 01 | 0 | 0 | 0 | 0 |
| 0 | 10 | 0 | 0 | 0 | 0 |
| 0 | 11 | 0 | 0 | 0 | 0 |
| 1 | 00 | 1 | 0 | 0 | 0 |
| 1 | 01 | 0 | 1 | 0 | 0 |
| 1 | 10 | 0 | 0 | 1 | 0 |
| 1 | 11 | 0 | 0 | 0 | 1 |