Explain the NOR GATES - Microprocessor

The NOR GATE is an OR gate with the output inverted. Consequently the outputs of a NOR gate would have the opposite states as the outputs of an OR gate.

The output Q is true if NOT inputs A OR B is true: Q = NOT (A OR B). A NOR gate can have two or more inputs and its output is true if no inputs are true.

The Boolean and symbol expression for a 3-input NOR gate is shown below.

The NOR gate will have a high output providing all of the inputs are low. Shown underneath is the truth table for a NOR gate. A simple way to derive the outputs for a NOR gate is to start with the truth table for an OR gate and invert all the outputs.