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The well-known 800 x 600 computer resolution standard simply means that
there are 800 pixels/line visible horizontally and there are 600 lines visible
vertically.
This item provides a way to change the number of active pixels and lines.
There is a period of time between the end of the Horizontal Sync pulse and
the start of Active Video. This portion of the waveform signal is called the
“Back Porch”, a term originating with the television broadcasting industry and
its RS-170A specification. In practice, this will control where the video image
starts on the left side of the monitor without changing the width of the sync
pulse itself (another way to control where the image area starts). The two
parameters control where the back porch is positioned and they interact to a
degree.
By adjusting these parameters, you control the start of the back porch (with
respect to the trailing edge of Horizontal Sync) and also its width. The place
where the Back Porch begins with respect to the Horizontal Sync pulse and
the width of the Back Porch have a direct bearing on where the active (visible)
portion of the image begins. Do not attempt this adjustment without monitoring
the results with an oscilloscope.
There are standards for all current computer and broadcast resolutions that
specify the correct width of both Vertical and Horizontal synchronizing pulses.
If you are creating a special, non-standard resolution, you may wish to adjust
the pulse width to fit your new requirements. The H/V Sync screen is where
that is accomplished.
Like the H/V Start adjustment, you must use an oscilloscope when making
these adjustments so that you know exactly how many milliseconds or
microseconds of pulse width you have created. The numbers shown are
relative numbers and not an actual time measurement.
Sync can be either negative polarity or positive polarity. To further complicate
things, it is possible that you may want to make the Horizontal Sync polarity
different from the Vertical Polarity. This control allows you to make that
change. You have four possible selections:
+H+V
-H+V
800 x 600 60 Hz
H/V Start [ 88] x 23
800 x 600 60 Hz
H/V Sync [ 128] x 4
800 x 600 60 Hz
Sync polarity [+H+V]
Summary of Contents for C2-7100
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