DVI Pins for the I2C DDC Bus Explained

The Digital Visual Interface (DVI) standard utilizes the Display Data Channel (DDC) to enable communication between a display device and a host graphics adapter. This system relies on a standard I2C serial bus protocol to transmit Extended Display Identification Data (EDID), allowing the system to automatically identify supported display modes and resolutions. Within the physical DVI connector, specific dedicated pins are assigned to manage the clock, data, power, and ground lines required for this bidirectional I2C interface.

Primary I2C DDC Bus Pins

The I2C protocol requires two primary signal lines to transmit information: serial clock (SCL) and serial data (SDA). On a standard 24-pin or 29-pin DVI connector (DVI-D, DVI-I, single-link, or dual-link), these signals are mapped directly to the following pins:

• Pin 6 – DDC Clock (SCL): This pin carries the I2C clock signal generated by the host graphics adapter. It synchronizes the transmission of data between the graphics card (the bus master) and the display's internal EEPROM (the bus slave).
• Pin 7 – DDC Data (SDA): This pin serves as the bidirectional line carrying serial data. The host requests identification records across this pin, and the display responds by transmitting its EDID structure.

Complementary DDC Support Pins

For the I2C bus to function independently of the monitor’s main power state, the DVI standard reserves two auxiliary pins that complete the DDC circuit:

• Pin 14 – +5V Power: The host provides a low-amperage 5-volt supply on this pin to power the display's configuration EEPROM. This allows the computer to read the monitor’s capabilities even when the display is switched off or disconnected from mains power.
• Pin 15 – Ground: This pin provides the dedicated ground return path for the +5V line, the DDC signals (Pins 6 and 7), and the analog sync signals on DVI-I connections.