Encoder

ENCODER

Encoder is a combinational circuit which is designed to perform the inverse operation of the decoder. An encoder has n number of input lines and m number of output lines. An encoder produces an m bit binary code corresponding to the digital input number. The encoder accepts an n input digital word and converts it into an m bit another digital word.

Block diagram

Examples

Priority Encoder

This is a special type of encoder. Priority is given to the input lines. If two or more input line are 1 at the same time, then the input line with highest priority will be considered. There are four input D₀, D₁, D₂, D₄ and two output Y₀, Y₁. Out of the four input D₃ has the highest priority and D₀ has the lowest priority. That means if D₃ = 1 Y, = 1 then Y₁ Y₁ = 11 irrespective of the other inputs. Similarly if D₃ = 0 and D₂ = 1 then Y₀ Y₁ = 10 irrespective of the other inputs.

Block diagram

Truth Table

Logic Circuit

Representation of logical function

Implement two following function using logical gates F = Ā B+ AB

Term 1 = Ā B → AND gate

Term 2 = AB AND gate

F = Term 1 + Term 2

Logical diagram

Truth Table