Glossary Definition for Tri-State

Definition

An output with three electrical states: One, zero, and "Hi-Z," or "open." The hi-Z state is a high-impedance state in which the output is disconnected, leaving the signal open, to be driven by another device (or to be pulled up or down by a resistor provided to prevent an undefined state).

Commonly used for a bus, in which any several devices can be selected. If the bus has a pull-down resistor, the tri-state arrangement achieves an OR function, dubbed "wired-OR."

Tri-State is a trademark of National Semiconductor.

Synonyms

• wired-OR
• hi-Z
• open collector
• open-drain

See Also

• Impedance
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