Q. Illustrate the working of Encoders?

An Encoder performs reverse function of decoder. An encoder has 2n input lines and 'n' output line. Let's see 8 ×3 encoder that encodes 8 bit information and generates 3 outputs consequent to binary numbers. This kind of encoder is also known as octal-to- binary encoder. Truth table of encoder is displayed in figure below.

Figure:   Encoder

From encoder table it's obvious that at any given time just one input is presumed to have 1 value. This is a main limitation of encoder. What would happen when two inputs are together active? The evident answer is since the output isn't defined ambiguity exists. To keep away this ambiguity encoder circuit has input priority so that just one input is encoded. The input with high subscript can be provided higher priority. For illustration if both D2 and D6 are 1 at same time then output will be 110 since D6 has higher priority than D2.Eencoder can be implemented with 3 OR gates whose inputs can be decided from truth table. Output can be represented as: 

O₀   = I₁ + I₃ + I₅ + I₇

O₁   = I₂ + I₃ + I₆ + I₇

O₂   = I₄ + I₅ + I₆ + I₇

You can draw K-Maps to conclude above functions as well as draw related combinational circuit.