13-04-2013, 04:24 PM
DESIGN AND IMPLEMENTATION OF ENCODER AND DECODER
AIM:
To design and implement the 8:3 encoder and 3:8 decoder using digital logic gates.
THEORY:
ENCODER:
An encoder is a digital circuit that performs inverse operation of a decoder. An encoder
has 2n input lines and n output lines. In encoder the output lines generates the binary code
corresponding to the input value. In octal to binary encoder it has eight inputs, one for each octal
digit and three output that generate the corresponding binary code. In encoder it is assumed that
only one input has a value of one at any given time otherwise the circuit is meaningless. It has an
ambiguity that when all inputs are zero the outputs are zero. The zero outputs can also be
generated when D0 = 1.
DECODER:
A decoder is a multiple input multiple output logic circuits which converts coded input
into coded output where input and output codes are different. The input code generally has fewer
bits than the output code. Each input code word produces a different output code word i.e. there
is one to one mapping can be expressed in truth table. In the block diagram of decoder circuit the
encoded information is present as n input producing 2n possible outputs. 2n output values are
from 0 through out 2n – 1.
PROCEDURE:
1. Connections are given as per the circuit diagram on the bread board.
2. The power supply is switched ON and set a voltage of 5 Volts.
3. If the input to be given to a gate is logic ‘1’ then it is connected to +5 Volts and if the input to be given to the gate is logic ‘0’ then the particular input terminal is connected to ground.
4. Truth tables of 8:3 encoder and 3:8 decoder are verified.
5. If the output is logic ‘1’ then the LED glows, if the output is logic ‘0’ then the LED does not glow.