Tri-State Buffer

Use DigiSim's active-HIGH Tri-State Buffer to drive LOW or HIGH when enabled and release its output to high impedance (Z) when disabled.

Overview

The Tri-State Buffer drives its data input when enabled and releases its output to high impedance when disabled. EN is active HIGH.

DigiSim Interface

Direction	Pin	Behavior
Input	D	One-bit data input.
Input	EN	Active-HIGH output enable.
Output	Y	Driven data or released `Z`.

Truth Table

A driven-unknown EN produces driven X; a released EN samples as LOW and releases Y. With EN HIGH, a released D samples as LOW and a driven-unknown D produces driven X.

Bus Use and Boundary

Coordinate enables so the intended source drives a shared net. Equal active drivers resolve to the same value, while conflicting LOW and HIGH drivers resolve to driven unknown X. Z is a logical release state; the model does not assign it an impedance magnitude or model current, voltage, loading, or electrical damage.

Learning Path

Prerequisites

Buffer AND Gate

Next Steps

8-Bit Tri-State Buffer 8-Bit Data Bus

Frequently Asked Questions

What is a tri-state buffer?

A tri-state buffer has three output states: HIGH (1), LOW (0), and high impedance (Z). When disabled, it does not drive the bus, allowing another enabled device to control the shared lines.

What is the high impedance state?

High impedance (Z) means this modeled output contributes no driven logic value. Another enabled source may then determine the net; simultaneously driving conflicting LOW and HIGH values creates contention rather than valid sharing.