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Browse Prior Art Database

Low-Cost Frequency Indication Technique for Multiscanning Monitors

IP.com Disclosure Number: IPCOM000114192D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 162K

Publishing Venue

IBM

Related People

Eagle, D: AUTHOR [+5]

Abstract

Described is a low-cost technique which may be used in a multiscanning monitor's design to allow the user to determine a display's horizontal and vertical scanning rates for a particular application.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Low-Cost Frequency Indication Technique for Multiscanning Monitors

      Described is a low-cost technique which may be used in a
multiscanning monitor's design to allow the user to determine a
display's horizontal and vertical scanning rates for a particular
application.

      Before the advent of multiscanning monitors, PCs and their
monitors only supported a handful of screen modes.  These ran at a
very limited and strictly specified set of horizontal and vertical
scan rates.  This has all changed with the advent of programmable
video adaptor cards, multiscanning monitors and flexible applications
and operating systems.  It is now possible for a PC/monitor
combination to operate over a very wide range of scanning
frequencies, typically 30-64KHz horizontally and 50-100Hz vertically.
The result is that many inexperienced users operate their monitors in
a non-optimum low resolution/low refresh rate mode.  This gives rise
to dissatisfaction from users.  The problem is how to enable users to
easily check which mode they are using.

      Two conventional solutions will now be described.  Both
indicate the resolution and scan rates to the user but are relatively
expensive.  The first solution is to have a small LCD panel on the
front of the monitor which displays this information.  The panel is
typically connected to the monitor's microprocessor by an I2C bus.
The second solution is to use 'on-screen display', superimposing the
information on top of the video image upon request.  Both of these
solutions are very effective but are relatively expensive.  The new
solution is a simple, low cost method of supplying just the key
information to the user.

      The basic idea is to display on the screen a series of
horizontal and/or vertical bars.  The user then counts these bars and
by reference to a look up table (provided in the monitor's "User's
Guide") is able to determine the horizontal and vertical scan rates
that he is using.  It is anticipated that these bars would be
generated in one of two different ways.  Firstly, they could be
generated directly by the monitor's microprocessor (which knows the
scan rates by constantly measuring the frequency of the incoming sync
signals).  Alternatively, they could be generated by simple external
circuitry.

      Consider the external circuitry case first.  The simplest
implementation would involve circuitry producing a series of bars
whose separation/width are fixed in terms of time and are independent
of the monitor's scanning frequencies.  The number of bars (either
vertical or horizontal) visible on a screen is hence related to the
horizontal and/or vertical scan rate - the more bars that are
visible, the lower the scan rate.  The bars could be either lines or
solid bars and could be made to be coloured to simplify counting.  It
is envisaged that the monitor's 'Users Guide' would contain a simple
table relating 'bar count' to scan frequency for both horizontal a...