Digital Circuits/Encoders-Decoders

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Encoders and decoders are similar to multiplexers and demultiplexers, except that they are a little bit more complicated.

Decoders[edit]

Decoders will have N inputs, and 2^N output. Let's say that we have two inputs (A and B), and 4 outputs (M N O P). Decoders will satisfy the following truth table:

A B M N O P
0 0 1 0 0 0
0 1 0 1 0 0
1 0 0 0 1 0
1 1 0 0 0 1

Binary numbers come in, and essentially select which wire to send a signal on.

Encoders[edit]

Encoders work in exactly the opposite way as decoders, taking 2^N inputs, and having N outputs. When a bit comes in on an input wire, the encoder outputs the physical address of that wire.It takes 2^n inputs and gives out n outputs,the enable pin should be kept 1 for enabling the circuit.


Priority Encoders[edit]

A Priority Encoder works opposite of the decoder circuit. Priority Encoders have logical ranking within them, input_1 may be higher than input_2. If input_2 and input_1 were pressed, the encoder would determine the priority, and accept the input.

Encoders and Multiplexers[edit]

The relationship between the two.

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