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DECODERBy Pradipta

WHAT IS DECODER ?

A decoder is a logic circuit that accepts a set of inputs that represents a binary

number and activates only the output the corresponds to the input number.

BASIC OF DECODER

Decoders are circuits with two or more inputs and one or more outputs, resulting by combining various types of gates. Their basic function is to accept a binary word (code) as an input and create a different binary word as an output .A decoder is a device which does the reverse operation of an encoder, Lets say we have N inputs to a decoder, the number of outputs will be equal to 2^N. Thus there will be one line at the output for each possible input.

How can we use them ?

Decoders are simply a collection of logic gates which are arranged in a specific way so as to breakdown any combination of inputs to a set of terms that are all set to '0' apart from one term. Therefore when one input changes, two output terms will change.

EXAMPLE

A co mmo n type o f de co de r is the line de co de r which take s an n-dig it binary numbe r and de co de s it into 2 n data line s. The simple st is the 1 -to -2 line de co de r. The truth table is

A D1 D0

100

1 1 0

EXAMPLE

A is the addre ss and D is the dataline . D0 is NOT A and D1 is A. The circuit lo o ks like

A D1

D0

EXAMPLE

A is the addre ss and D is the dataline . D0 is NOT A and D1 is A. The circuit lo o ks like

A D1

D0