Encoders and Decoders
Download
Report
Transcript Encoders and Decoders
Encoders
Decoders
Example of using decoders with MUX
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.
Other reasons for using encoders include:
data encryption for making the data secure
translating data from one code to another new or
existing code.
Encoders may be analog or digital devices.
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
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
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
Encoders
Decoders
Example of using decoders with MUX
Conclusion
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.
A decoder chooses one of the wires and make it
output 1.
The output whose index is given by the binary
value on S (select input) is set to 1. All others are
set to 0.
Only one wire can be ‘ON’ at a time.
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
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
Encoders
Decoders
Example of using decoders with MUX
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
Encoders
Decoders
Example of using decoders with MUX
Conclusion
If the encoders are the opposite of decoders,
then that means that the outputs and inputs
of the decoder are swapped.
That means that what would normally be the
select lines on the decoder (which are inputs)
would now be the outputs of the encoder.
Its purpose would be to produce the binary
encoding of the index whose input is high.
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.
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.