TCL LCD32M61S3-MS19, Service Manual

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Part VI HDMI EDID Introduction
Extended display identification data (EDID) is a data structure provided by a
computer display to describe its capabilities to a graphics card. It is what enables
a modern personal computer to know what kind of monitor is connected. EDID is defined
by a standard published by the Video Electronics Standards Association (VESA). The
EDID includes manufacturer name, product type, phosphor or filter type, timings
supported by the display, display size, luminance data and (for digital displays
only) pixel mapping data.
The channel for transmitting the EDID from the display to the graphics card is usually
the I
2
C bus. The combination of EDID and I²C is called the Display Data Channel version
2, or DDC 2. The 2 distinguishes it from VESA's original DDC, which used a different
serial format.
Before DDC and EDID were defined, there was no standard way for a graphics card to
know what kind of display device it was connected to. Some VGA connectors in personal
computers provided a basic form of identification by connecting one, two or three
pins to ground, but this coding was not standardized.
The EDID is often stored in the monitor in a memory device called a serial PROM
(programmable read-only memory) or EEPROM (electrically erasable PROM) that is
compatible with the I²C bus.