Some explanations for oscillators with tri-state functions (Pin 1)

Three-state, or Tri-State

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).

High-impedance schemes such as three-state are commonly used for a bus, in which several devices can be selected to drive the bus.

Hi-Z (or High-Z or high impedance)

Hi-Z (or High-Z or high impedance) refers to an output signal state in which the signal is not being driven. The signal is left open, so that another output pin (e.g. elsewhere on a bus) can drive the signal or the signal level can be determined by a passive device (typically, a pull-up resistor).

Impedance

Impedance, represented by the symbol Z, is a measure of the opposition to electrical flow. It is measured in ohms.

For DC systems, impedance and resistance are the same, defined as the voltage across an element divided by the current (R = V/I).

In AC systems, the “reactance” enters the equation due to the frequency-dependent contributions of capacitance and inductance. Impedance in an AC system is still measured in ohms and represented by the equation Z = V/I, but V and I are frequency-dependent.