Three-state logic
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- See also: Tri-state area, tripoint.
In electronics a three-state, tri-state or 3-state digital logic allows output ports to have a value of 0, 1, or Z. A Z output stands for the output port being disconnected from the rest of the circuit, putting the output in a high impedance state. The intent of this state is to allow multiple circuits to share the same output line or bus without affecting each other.
3-state outputs are implemented in various families of digital integrated circuits such as the 7400 series of TTL gates, and often in the data and address bus lines of microprocessors.
A common synonym is tristate logic, which is a registered trademark of National Semiconductor.
This form of gate should not be confused with 3-value logic (ternary logic).
