View source for Wired-OR

'''Wired-OR''' refers to a common technique which uses no active devices to perform the [[logic]] function; it wires together the outputs of multiple [[open collector]] [[gate]]s to do it, using [[negative logic]].

It connects together the outputs of the gates which produce the signals which are to be ORed together; a pull-up [[resistor]] to the supply [[voltage]] completes the 'gate'. Since [[transistor-transistor logic|TTL]] gates produce low outputs by sinking [[current]] to [[ground]] (drawing it ''into'' the gate through the output, seemingly paradoxically), any of the gates in the wired-OR can force the output low by turning on.

(This method is often used to implement [[broadcast]] lines on a [[bus]].)

Similarly, this technique allows the creation of so-called '''wired-AND''' in [[positive logic]]; if any of the inputs to the 'AND' is low, it force the output low - i.e. a logical AND.

[[Category: Technology]]