DVI Connector TMDS Clock Pinout Explained

This article identifies the exact pin configuration for the TMDS Clock- line on a standard Digital Visual Interface (DVI) connector. It outlines the pin assignment, explains the function of the TMDS differential clock signaling system, and details the layout of related clock pins found across single-link and dual-link DVI ports.

Exact Pin Number for TMDS Clock-

In any digital DVI connector (DVI-D or DVI-I), the exact pin number for TMDS Clock- is Pin 24.

Pin 24 carries the negative (inverted) component of the differential clock pair used to synchronize the transmission of digital video data.

DVI Clock Pin Mapping

Transition-Minimized Differential Signaling (TMDS) uses twisted pairs to carry high-frequency signals with minimal electromagnetic interference. The clock signal is distributed across three designated pins located at the bottom-right corner of the standard 24-pin DVI grid:

  • Pin 22: TMDS Clock Shield (Ground return for the clock pair)
  • Pin 23: TMDS Clock+ (True/non-inverted clock signal)
  • Pin 24: TMDS Clock- (Inverted clock signal)

Function of TMDS Clock-

The TMDS Clock- (Pin 24) works directly in tandem with TMDS Clock+ (Pin 23). Instead of measuring a single signal relative to ground, the receiving display measures the voltage difference between Pin 23 and Pin 24.

This differential signaling approach allows external noise affecting the cable to impact both conductors equally, enabling the receiver to cancel out the interference. The clock operates at the character rate (one-tenth the data rate in single-link mode) to ensure the receiver correctly decodes the red, green, and blue TMDS data channels.

Connector Compatibility

Pin 24 occupies the same physical location and performs the same function across all major digital DVI variants:

  • DVI-D Single-Link: 18 digital pins (Pins 4, 5, 12, 13, 20, and 21 omitted; Pin 24 remains TMDS Clock-)
  • DVI-D Dual-Link: Full 24 digital pins (Pin 24 is TMDS Clock-)
  • DVI-I Single-Link / Dual-Link: Integrated digital pins plus 4 analog pins (Pin 24 remains TMDS Clock-)

Regardless of whether the connector is single-link or dual-link, TMDS Clock- is consistently wired to Pin 24.