1 Answers
In digital electronics three-state, tri-state, or 3-state logic allows an output or input pin/pad to assume a high impedance state, effectively removing the output from the circuit, in addition to the 0 and 1 logic levels.
This allows multiple circuits to share the same output line or lines.
Three-state outputs are implemented in many registers, bus drivers, and flip-flops in the 7400 and 4000 series as well as in other types, but also internally in many integrated circuits. Other typical uses are internal and external buses in microprocessors, computer memory, and peripherals. Many devices are controlled by an active-low input called OE which dictates whether the outputs should be held in a high-impedance state or drive their respective loads.
The term tri-stateshould not be confused with ternary logic.