NOR logic

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This article is about NOR Logic in the sense of building other logic gates using just NOR gates. For information on NOR gates, see NOR gate. For NOR in the purely logical sense, see Logical NOR. For logic gates in general, see Logic Gate.
a simple NOR gate
a simple NOR gate

Like NAND gates, NOR gates can be combined to form any other kind of logic gate.

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[edit] NOT

A NOT gate is made by joining the legs of a NOR gate. This is because A and B are then always equal, and the NOR will act as an inverter.

Input Input A Input B Output
0 0 0 1
1 1 1 0
Desired Gate NOR Construction
Image:NOR NOT.PNG

[edit] OR

An OR gate is made by inverting the output of a NOR gate through a NOR gate connected as a NOT gate.

Input A Input B Normal
Output		 Inverted
Output
0 0 1 0
0 1 0 1
1 0 0 1
1 1 0 1
Desired Gate NOR Construction
Image:NOR OR.PNG

[edit] AND

An AND gate is made by connecting the output of 2 NOR gates (connected as NOT gates) to the respective inputs of a NOR gate.

Input A Input B Inverted
Input A		 Inverted
Input B		 Output
0 0 1 1 0
0 1 1 0 0
1 0 0 1 0
1 1 0 0 1
Desired Gate NOR Construction
Image:NOR AND.PNG

[edit] NAND

A NAND gate is made by inverting the output of 3 NOR gates (connected as an AND gate) through a NOR gate connected as an inverter.

Input A Input B Normal
Output		 Inverted
Output
0 0 0 1
0 1 0 1
1 0 0 1
1 1 1 0
Desired Gate NOR Construction
Image:NOR NAND.PNG

[edit] XOR

An XOR gate is made by connecting the output of 3 NOR gates (connected as an AND gate) and the output of a NOR gate to the respective inputs of a NOR gate.

Input A Input B Output A Output B Output
0 0 0 1 0
0 1 0 0 1
1 0 0 0 1
1 1 1 0 0
Desired Gate NOR Construction
Image:NOR XOR.PNG

Alternatively, an XOR can be implemented in 5 gates by using the 4-gate version of XNOR combined with another NOR used as an inverter.

[edit] XNOR

An XNOR gate can be constructed from four NOR gates implementing the expression "(A NOR N) NOR (B NOR N) where N = A NOR B".

Desired Gate NOR Construction
Image:NOR XNOR in four gates.png

Alternatively, an XNOR gate is made by inverting the output of 5 NOR gates connected as an XOR gate through a NOR gate connected as an inverter.

Input A Input B Normal
Output		 Inverted
Output
0 0 0 1
0 1 1 0
1 0 1 0
1 1 0 1
Desired Gate NOR Construction
Image:NOR XNOR.PNG

[edit] See also