active-high

Understanding Active-High Logic Signals: The Language of Electronics

In the world of electronics, logic signals are the building blocks of communication. These signals represent binary information (0 or 1), and their interpretation is crucial for the operation of digital circuits. One key concept in understanding logic signals is their active state. This refers to the state in which the signal is considered "on," "asserted," or "true."

Active-High signals are a common type of logic signal where the logic ONE state (1) represents the active, asserted, or true condition. This means:

1. The Logic ONE State is the Asserted State:

• When an active-high signal is in the logic ONE state (1), it is considered active or asserted. This signifies a particular condition is true, an action is being performed, or a function is enabled.
• Conversely, the logic ZERO state (0) indicates an inactive, unasserted, or false condition.

2. The Logic ONE State is the Higher Voltage:

• Active-high signals typically use higher voltage to represent the logic ONE state and lower voltage for the logic ZERO state. This is common in traditional CMOS (Complementary Metal-Oxide Semiconductor) technology, where a higher voltage level indicates a logic 1 and a lower voltage indicates a logic 0.

Examples of Active-High Signals:

• Push-button Switches: A push-button switch is often active-high. When the button is pressed, it closes the circuit, resulting in a higher voltage (logic 1), indicating the button is pressed.
• Digital Logic Gates: In many logic gates, like AND gates and OR gates, a logic ONE input is required to activate the gate and produce a logic ONE output.
• Microcontroller Pins: Microcontroller pins are often configured as active-high outputs. When a pin is set to logic HIGH, it drives a signal to a higher voltage level, typically to activate an external device.

Active-High vs. Active-Low:

It's important to understand that the opposite of active-high is active-low, where the logic ZERO state (0) is the active state. Active-low signals are used in certain situations, especially when inverting logic is desired or when utilizing a negative logic system.

Understanding active-high and active-low signals is essential for correctly interpreting and manipulating logic signals in electronic circuits. By knowing the active state of a signal, you can understand the intended behavior of the circuit and predict how it will respond to different inputs.