1) In
an encoder is a digital circuit that perform the inverse operation of decoder.
2) An encoder is a combinational
circuit which has 2n input lines and n output lines.
3) The output lines generate the
corresponding binary value for the input.
4) The example for encoder is to
binary conversion.
5)The encoder can be represented
in the input output combination as shown below.
6)The
encoder can be represented by using OR gate for which we can get the output from the truth table.
7)Here there are 3 outputs X,Y, Z and
8 inputs DO,D1,D2,D3,D4,D5,D6,D7.
8)The output X is represented by
D4,D5,D6 and D7.
9)The output Y can be represented by
using D2,D3,D6,D7.
10)The output Z can be represented by using
D1,D3,D5,D7.
11)We can represent X,Y,Z from the truth
table as shown below
X=D4+D5+D6+D7
Y=D2+D3+D6+D7
Z=D1+D3+D5+D7
12)The encoder can be represented by using
OR gate as shown below
13)The above circuit is also known as
octal to binary encoder.
14) The problem in above encoder is that
generally the output will be zero when all the inputs are zero whereas in
encoder the output is zero when one of the input line D0 is 1.
15)To
overcome the above limitation the priority encoder is designed.
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