Encoders and Decoders Content to be covered Encoders

Encoders and Decoders

Content to be covered: �Encoders �Decoders �Example of using decoders with MUX �Conclusion

ENCODERS �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 �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

ENCODERS vs MULTIPLEXORS �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.

Example of an ENCODER Inputs Output

Activity Draw: 1. 2 input encoder 2. 4 input encoder 3. 16 input encoder

Further example of Encoders � If in an encoder the following input was given, the output/address would be as indicated: A B C D E F G H S 0 S 1 S 2 1 0 0 0 0 0 0 0

Further example of Encoders �If in an encoder the following input was given, the output/address would be as indicated: A B C D E F G H S 0 S 1 S 2 0 0 0 1 0 1 1 0 1

Content to be covered: �Encoders �Decoders �Example of using decoders with MUX �Conclusion

DECODERS �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.

DECODERS �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).

Example of a DECODER Output NB: Only ONE of the line will have the value 1; others will have 0.

Activity Draw: 1. 1 input decoder 2. 2 input decoder 3. 4 input decoder

Further example of Decoders �If in a decoder the following selects were made, the output would be as indicated: S 0 S 1 S 2 A B C D E F G H 1 0 0 0 1 0 0 0

Further example of Decoders �If in a decoder the following selects were made, the output would be as indicated: S 0 S 1 S 2 0 1 0 A B C D E F G H 0 0 1 0 0 0

Content to be covered: �Encoders �Decoders �Example of using decoders with MUX �Conclusion

Example of using decoders with MUX

Example of using decoders with MUX • The decoder selected 01, which allows 01 to be set to 1, hence allowing it to light up. • The MUX gets input from the wire that has been lit-up by the decoder.

Example of using decoders with MUX • 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.

Example of using decoders with MUX 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.

Activity 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

Content to be covered: �Encoders �Decoders �Example of using decoders with MUX �Conclusion

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 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.

Conclusion �That is, the encoder will have 2 n 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.

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