Acer AT2001 Service Manual page 24

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VESA DDC

The VGA input shall be capable of continuously transmitting its Extended Display Identification (EDID)

information using Display Data Channel. It shall automatically switch to DDC2 mode if a DDC2 capable

host is detected in accordance with the VESA DDC standard.

In addition, the display can respond to a request for EDID, to be transmitted using DDC2, level B

commands. If a DDC2 capable host is detected by the display, the display shall switch to DDC2

communication.

The EDID shall contain the manufacture name code QCI, product code, date of manufacture, and serial

number.

For complete EDID data structure, please refer to VESA Extended Display Identification Data

Standard.

Hardware implementation may be either integrate into micro-controller or be a separate electrical

component. EDID memory must be protected against writing or other corruption through customer-

accessible electrical connection and required communication channels. Password protection, use of an

unpublished enable register, or use of direct electrical connection is acceptable levels of protection provided

that the power-on Default State is that disabling writing. The serial number fields in the EDID must contain

a unique identifying numbers among units of the same model. EDID Table is defined as below:

For VGA input :

128 BYTES OF EDID CODE

------------------------------------------------------------

100

110

120

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