| .model top | |
| .inputs cin a0 a1 b0 b1 | |
| .outputs s0 s1 cout | |
| .names cin a0 a1 b0 b1 s1 | |
| 000-1 1 | |
| 001-0 1 | |
| 0-001 1 | |
| 0-100 1 | |
| 110-0 1 | |
| 111-1 1 | |
| 1-010 1 | |
| 1-111 1 | |
| -0001 1 | |
| -0100 1 | |
| -1010 1 | |
| -1111 1 | |
| .names cin a0 b0 s0 | |
| 001 1 | |
| 010 1 | |
| 100 1 | |
| 111 1 | |
| .names cin a0 a1 b0 b1 cout | |
| 111-- 1 | |
| 11--1 1 | |
| 1-11- 1 | |
| 1--11 1 | |
| -111- 1 | |
| -1-11 1 | |
| --1-1 1 | |
| .end |