SVGA Monitor Identification Bits`

[webpa]

I give up: How does a Sony (FX-140) notebook recognize the presence of
an external (VGA/SVGA) monitor? Many Google hits on the topic provide
monitor ID bit identifications...and variations thereon. But NONE of
them seem to work. That is: Grounding the indicated pins, in all
possible combinations, does not cue the computer that a monitor is
connected. It cannot be that the FX-140 requires active communication
with a monitor, because the computer recognizes ANY connected monitor
(have tried 5) whether they are powered or not.

Any hints? Diodes between pins...resistors...holy water?

 

[Bob Myers]

I give up: How does a Sony (FX-140) notebook recognize the presence of
an external (VGA/SVGA) monitor? Many Google hits on the topic provide
monitor ID bit identifications...and variations thereon. But NONE of
them seem to work. That is: Grounding the indicated pins, in all
possible combinations, does not cue the computer that a monitor is
connected. It cannot be that the FX-140 requires active communication
with a monitor, because the computer recognizes ANY connected monitor
(have tried 5) whether they are powered or not.

Any hints? Diodes between pins...resistors...holy water?

Monitor ID pins haven't been used for a LONG time.
The ID solution used today is a VESA standard called the
Display Data Channel (DDC), which is based on the
I2C electrical interface. There are two pins on the VGA
connector which support the DDC, one clock and one
serial data, and the PC reads a 128-byte file called the
EDID (Extended Display Identification Data) over this
connection. You can no doubt get more information on
this system by Googling for "DDC" and "EDID".

The simple presence of the monitor is also sometimes
sensed by noting whether or not there is a load on any
of several lines on the VGA output, including the RGB
video pins (pins 1, 2, and 3) or the +5 VDC pin that is
also provided under the DDC standard (pin 9).

Bob M.