4x2 Encoder
Encoders work in exactly the opposite way as decoders, taking inputs, and having N outputs. When a bit comes in on an input wire, the encoder outputs the physical address of that wire. It takes $$2^n$$ inputs and gives out n outputs, the enable pin should be kept 1 for enabling the circuit.
2x4 encoder symbol
2x4 encoder circuits
2x4 encoder truth table
| Q0 | Q1 | Q2 | Q3 | A | B |
|---|---|---|---|---|---|
| 0 | 0 | 0 | 1 | 0 | 0 |
| 0 | 0 | 1 | 0 | 0 | 1 |
| 0 | 1 | 0 | 0 | 1 | 0 |
| 1 | 0 | 0 | 0 | 1 | 1 |