Which TMDS Channel Carries Red in DVI?

In a Digital Visual Interface (DVI) connection, video data is transmitted using Transition-Minimized Differential Signaling (TMDS). This article outlines the specific channel mapping used in DVI, directly identifying which TMDS data channel carries the red color component and explaining how standard RGB video signals are distributed across the interface.

The TMDS Channel for Red Color Data

In standard single-link DVI, TMDS Data Channel 2 carries the red color data.

DVI relies on serial transmission to send uncompressed digital video from a graphics controller to a display. Standard 24-bit RGB video (8 bits per channel) is serialized and distributed across three independent TMDS data channels, accompanied by a fourth channel dedicated to the pixel clock.

TMDS Channel Assignments in DVI

To understand the architecture, the complete mapping of primary TMDS channels in a standard single-link DVI connection is defined as follows:

  • TMDS Data Channel 0: Transmits the Blue color data, as well as the Horizontal Sync (HSync) and Vertical Sync (VSync) signals during the blanking intervals.
  • TMDS Data Channel 1: Transmits the Green color data, along with control signals CTL0 and CTL1 during blanking periods.
  • TMDS Data Channel 2: Transmits the Red color data, along with control signals CTL2 and CTL3 during blanking periods.
  • TMDS Clock Channel: Transmits a continuous differential reference clock signal used to synchronize the receiver with the incoming data streams.

Pinout Mapping for Channel 2

On a physical DVI connector (both DVI-D and DVI-I), TMDS Data Channel 2 operates over a shielded twisted pair corresponding to the following pin assignments:

  • Pin 1: TMDS Data 2- (negative differential line)
  • Pin 2: TMDS Data 2+ (positive differential line)
  • Pin 3: TMDS Data 2/4 Shield (ground shield)

In dual-link DVI configurations, which are designed to support higher resolutions and refresh rates, a second set of data channels is added. In that scenario, TMDS Data Channel 5 is paired with Channel 2 to carry the additional red color data bits for the second link. However, for primary single-link communication and standard color distribution, Channel 2 remains the designated carrier for red color information.