An XNOR (exclusive NOR) gate is a fundamental binary logic gate with two inputs and one output.
The output is `1`

only if both inputs are equal.
The equivalent logical connective is equivalence.
An XNOR gate with more than two inputs gives an output of `1`

if an even number of inputs is `1`

.
Some authors call the XNOR gate with N inputs the *even function*.

The following truth table gives the specification for a two input XNOR gate with output `X`

:

` A ` | ` B ` | ` X ` |
---|---|---|

`0` | `0` | `1` |

`0` | `1` | `0` |

`1` | `0` | `0` |

`1` | `1` | `1` |

The schematic form of the XNOR gate is:

Below is a Verilog structural model for the XNOR gate.
In the code, the first argument to `xnor`

is the gate output, the other arguments are inputs.

` ````
module xnor_gate(X, A, B);
output X;
input A;
input B;
xnor(X, A, B);
endmodule
```

Mano, M. Morris, and Kime, Charles R. *Logic and Computer Design Fundamentals. 2nd Edition.* Prentice Hall, 2000.

Kleitz, W. *Digital Microprocessor Fundamentals. 3rd Edition.* Prentice Hall, 2000.

Copyright © 2014 Barry Watson. All rights reserved.