DVI-I Horizontal Sync Pin Assignment

This guide provides a direct breakdown of the horizontal synchronization (H-Sync) pin assignment on a DVI-I (Digital Visual Interface – Integrated) connector. Because DVI-I carries both high-definition digital signals and legacy analog video, specific designated pins handle the RGB and synchronization channels. Below, you will find the exact pin location for the horizontal sync signal and its role within the DVI-I pinout architecture.

The Horizontal Sync Pin Location

On a standard DVI-I connector, the Analog Horizontal Sync signal is assigned to Pin C4.

A DVI-I connector features a main grid of 24 digital pins alongside a distinct analog cluster separated to one side. This analog cluster contains four pins surrounding a flat ground bar:

• Pin C1: Analog Red
• Pin C2: Analog Green
• Pin C3: Analog Blue
• Pin C4: Analog Horizontal Sync
• Pin C5: Analog Ground (the wide horizontal blade)

Pin Layout and Functionality

Pin C4 is located immediately below the flat ground blade (Pin C5) on the analog side of the connector, positioned on the outer vertical column.

When a DVI-I port outputs an analog signal—such as through a passive DVI-to-VGA adapter—Pin C4 transmits the horizontal synchronization pulses. These timing pulses dictate when a monitor completes a horizontal scan line and begins the next.

For the complete synchronization circuit, Pin C4 works in tandem with:

• Pin 8 (Analog Vertical Sync): Located in the main 24-pin grid at the end of the top row.
• Pin C5 (Analog Ground): Serves as the return path for both the RGB video and sync signals.

Because horizontal sync is an analog timing function, Pin C4 is only active when an analog display or adapter is in use. Digital DVI connections (DVI-D) do not utilize Pin C4, as timing data is embedded directly into the digital TMDS data streams.