Author: M Abo Bakar Aslam
2x1 Encoder and 1x2 Decoder
A 2-to-1 line Encoder and 1-to-2 lines Decoder are the simplest forms of encoding and decoding circuits used in digital systems.
1. Truth Table - 2x1 Encoder
Suppose inputs are A-0 and A-1 and output is Y.
Total Number of Rows = 2^(number of inputs) = 2² = 4
| A-1 | A-0 | Output (Y) |
|---|---|---|
| 0 | 1 | 0 |
| 1 | 0 | 1 |
2. Boolean Expression - 2x1 Encoder
Y = A-1
3. Truth Table - 1x2 Decoder
Suppose input is Y and outputs are A-0 and A-1.
Total Number of Rows = 2^(number of inputs) = 2¹ = 2
| Input (Y) | A-1 | A-0 |
|---|---|---|
| 0 | 0 | 1 |
| 1 | 1 | 0 |
4. Boolean Expression - 1x2 Decoder
A-0 = Y'
A-1 = Y
5. Circuit Diagram - Encoder and Decoder
Important Note
Encoder and Decoder are inverse operations. Encoder converts multiple inputs into fewer outputs, while Decoder expands a single input into multiple outputs.