Transcript Encoders and Decoders


Encoders

Decoders

Example of using decoders with MUX
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Conclusion

An encoder is a device that is used to convert a
signal or certain data into code.

This kind of conversion is done for a variety of
reasons, the most common being data
compression.
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Other reasons for using encoders include:
 data encryption for making the data secure
 translating data from one code to another new or
existing code.
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Encoders may be analog or digital devices.
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In analog devices, the encoding is done using
analog circuitry
While
in digital encoders the encoding is done
using program algorithms


An encoder refers to a device that is used to
change a signal or data into a code.
Whereas

A Multiplexer or mux is a device which
performs multiplexing or it takes information
from more than one channels and outputs
into a single channel.
Inputs
Output
Draw:
1. 2 input encoder
2. 4 input encoder
3. 16 input encoder
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If in an encoder the following input
was given, the output/address
would be as indicated:
A B C D E F G H S0 S1 S2
1 0 0 0 000 0 0 0 0
0
0
0
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If in an encoder the
following input was given,
the output/address would
be as indicated:
ABCDEFGH
0 0 0 0 010 0
S0 S1 S2
1 0 1
1
0
1
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Encoders

Decoders

Example of using decoders with MUX

Conclusion
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A decoder, on the other hand, functions the
reverse of an encoder.

It is a device that is used to decode an encoded
signal or data.

It does this to help retrieve the data that was
encoded in the first place.

Both encoders and decoders usually function in
cycle, i.e., an application that uses an encoder
would ideally also require a decoder.
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A decoder chooses one of the wires and make it
output 1.
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The output whose index is given by the binary
value on S (select input) is set to 1. All others are
set to 0.
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Only one wire can be ‘ON’ at a time.
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Whichever one is ‘ON’ is based on the input (ie
@ the selector).
Output
NB: Only ONE of the line
will have the value 1; others
will have 0.
Draw:
1. 1 input decoder
2. 2 input decoder
3. 4 input decoder

If in a decoder the
following selects were
made, the output
would be as indicated:
S0 S1 S2
1 0 1
0 1 0
ABCDEFGH
0 0 0 0 0100
0 0 1 0 0000
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If in a decoder the
following selects were
made, the output
would be as indicated:
S0 S1 S2
0 1 0
ABCDEFGH
0 0 1 0 0000
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Encoders

Decoders
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Example of using decoders with MUX
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Conclusion
•
The decoder selected 01,
which allows 01 to be set
to 1, hence allowing it to
light up.
•
The MUX gets its input
from the wire that has
been lit-up by the
decoder.
•
The input to the MUX of 1
or 0 is based on if the
lines are connected (1) or
disconnected (2).
•
In the example given
above, if the select for the
2-1 MUX is 00, the output
would be 0.
Please Note:
•
You don’t always have
equal rows and columns.
•
A decoder does not have
an output line, and the
input (which is to the
side) is the select lines.
Draw:
1. 2-4 Decoder with a 8-1 bit Mux
2. 1-2 Decoder with a 4-1 bit Mux
(using only 2-1 bit muxes) LOL
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Encoders

Decoders

Example of using decoders with MUX
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Conclusion
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If the encoders are the opposite of decoders,
then that means that the outputs and inputs
of the decoder are swapped.
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That means that what would normally be the
select lines on the decoder (which are inputs)
would now be the outputs of the encoder.
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Its purpose would be to produce the binary
encoding of the index whose input is high.
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That is, the encoder will have 2n inputs and n
outputs, and only one of the inputs is
expected to be high at any one moment.
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Encoders are useful for components like
content-addressable memory, where you put
in the data you want, and the address where
it is stored is returned as a result.