Digital systems

Decoder

A decoder is a combinational circuit that converts binary information from n input lines to a maximum of 2^n unique output lines. Decoders usually have an enable line, If enable = 0, decoder is off. It means all output lines are zero. If enable = 1, decoder is on and depending on input, the corresponding output line is 1, all other lines are 0.

Priority encoder

A priority encoder is an encoder circuit that includes a priority function.

Multiplexer

Combinational circuit that selects binary information from one of the input lines and directs it to a single output line. Usually there are 2^n input lines and n selection lines whose bit combinations determine which input line is selected.

Encoder

The encoder generates a unique binary code from several input lines. Generally, encoders produce 2-bit, 3-bit, or 4-bit code. An n-bit encoder has 2^n input lines. If one of the four input lines is active, encoder produces the binary code corresponding to that line. If more than one of the input lines will be activated, or if all the output lines are undefined, then we can consider don't care conditions

Comparator

The purpose of a Digital Comparator is to compare a set of variables or unknown numbers, for example A against that of a constant or unknown value such as B and produce an output condition or flag depending upon the result of the comparison. A=B, A<B, A>B