DDC and edid

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DDC and edid are the technical standards for display hardware. The earliest standards were born in 1994. The standard is simply to let the computer know the various specifications of the display (such as the supported resolution mode, supported refresh frequency, supported field frequency range, product model, A communication standard. In this way, when the monitor is connected to a computer, the system (Windows) can automatically set the monitor for the user, plug-and-play is enabled ).

DDC is short for the display data channel and is the communication standard between the display adapter and the display device. All information will be transmitted from the ROM in the monitor to the display card. This information is called edid (Extended display identification data ).

Of course, the information provided by edid is the various types supported by the display device (Display). If the display card is not supported, it will not be supported by the system at last. In additionProgramDetermines the behavior of the display card, so sometimes you need to upgrade the driver to support a specific display specification.

In Windows, the DDC function of the display card is used to obtain the list of supported display modes and resolutions.

 

1. DDC: Display Data Channel (display data channel)-refers to the communication mode between the host and the display device. Based on the end-user plug-and-play function requirements, Vesa defines the DDC standard. Including ddc1/ddc2b/ddc2b +.

Ddc1 is one-way communication between the host and the display device, with V-sync as clock. The monitor keeps sending edid information to the host.

Ddc2b is a quasi-bidirectional communication between hosts and display devices based on I2C communication protocol. Edid information is sent only when the host sends a request signal to the monitor and receives a response from the monitor.

Currently, ddc1 is basically no longer used, mainly in the ddc2b mode. Ddc1 cannot be used in pc2001.

2. edid: Extended display identification data (external display device identification data) ---- display device data transmitted in DDC communication.

Edid contains the basic parameters of the display device, such as the manufacturer, product name, the most frequently used field, and supported resolutions.

The edid version is upgraded from 1.0 to 1.3 to 2.0.

Version: 1.0. Version 1.1. version 1.2. Version 1.3.

128 byte current version 256 byte

The factory writes the edid into the eeprom or CPU Ram through the DDC burning program.

Edid: Extended display identification data (Extended display ID data) is a standard VESA data format that contains parameters related to the monitor and its performance, including supplier information, maximum image size, color settings, vendor pre-settings, frequency range restrictions, and strings of the display name and serial number. This information is stored in the Display Section and used to communicate with the system through a DDC (display data channel), between the display and PC graphics adapter. The latest version of edid can be used in CRT, LCD, and future display types, because edid provides a general description of almost all display parameters.

 

Http://en.wikipedia.org/wiki/Display_Data_Channel

Http://en.wikipedia.org/wiki/VGA_connector