Glossary Definition for Three-State

Definition

A three-state, or Tri-State™, output has 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

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

See Also

• Impedance
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