Puzzled?
Here's a ‘walk-through’ description of the schematic.
Here's a ‘walk-through’ description of the schematic.
Imagine ‘C1’ and ‘C2’ are both high: this ‘disconnects’ the pull-up tree and guarantees a pull down: else if ‘B1’ is low the other pull-down tree is disconnected and the pull-up asserted: else … you have a NOR gate remaining.
Truth table
| A1 | A2 | B1 | C1 | C2 | Q |
|---|---|---|---|---|---|
| – | – | – | 1 | 1 | 0 |
| – | – | 0 | 0 | – | 1 |
| – | – | 0 | – | 0 | 1 |
| 0 | 0 | – | 0 | – | 1 |
| 0 | 0 | – | – | 0 | 1 |
| 1 | – | 1 | 0 | – | 0 |
| – | 1 | 1 | 0 | – | 0 |
| 1 | – | 1 | – | 0 | 0 |
| – | 1 | 1 | – | 0 | 0 |