Browse Prior Art Database

Method to Detect Attach and Detach External Monitor

IP.com Disclosure Number: IPCOM000119209D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Kawano, S: AUTHOR [+4]

Abstract

Disclosed is a circuit and software for detecting attach and detach external monitor Cathode Ray Tube (CRT) dynamically without any setting by the user. The circuit causes hardware interrupt when the external CRT is attached into or detached from the port of a Personal Computer (PC), and notifies the software to select output device. Then the video driver of the operating system changes screen resolution. By using this function, the system can select the most suitable video output device, a Liquid Crystal Display (LCD) or the CRT, and change screen resolution to fit current display automatically and dynamically.

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Method to Detect Attach and Detach External Monitor

      Disclosed is a circuit and software for detecting attach and
detach external monitor Cathode Ray Tube (CRT) dynamically without
any setting by the user.  The circuit causes hardware interrupt when
the external CRT is attached into or detached from the port of a
Personal Computer (PC), and notifies the software to select output
device.  Then the video driver of the operating system changes screen
resolution.  By using this function, the system can select the most
suitable video output device, a Liquid Crystal Display (LCD) or the
CRT, and change screen resolution to fit current display
automatically and dynamically.

      Many portable PCs have external CRT port in addition to
built-in LCD panel.  Resolution of LCD panel is limited like 640x480
or 800x600.  The user can get higher resolution, like 1024x768 or
more, by attaching an external CRT.  On the conventional PCs, to
change screen resolution, user have to select resolution from setting
menu or restart the operating system.  By using function of this
circuit, the notebook PC system switches display output to CRT with
high resolution from built-in LCD automatically as soon as external
CRT is attached.  When CRT is detached, the system also switches
display output source to built-in LCD.

      Currently, wrap-back circuit in digital-analog converter is
used to detect presence of external CRT.  This method has following
weak points.
  o  Large overhead - it tak...