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James Gregory 2013-12-30 18:34:31 +11:00
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@ -3,8 +3,8 @@
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Listing 28.3 illustrates an efficient use of write mode 3 in conjunction
with read mode 1 and a Color Don’t Care register setting of 0. The mask
in AL is passed directly to the VGA’s bit mask (that’s how write mode 3
with read mode 1 and a Color Don't Care register setting of 0. The mask
in AL is passed directly to the VGA's bit mask (that's how write mode 3
works—see Chapter 4 for details). Because the VGA always returns 0FFH,
the single **AND** instruction loads the latches, and writes the value
in AL, unmodified, to the VGA, where it is used to generate the bit
@ -126,24 +126,24 @@ excellent pixel- and line-drawing code.
code ends
end Start
I hope I’ve given you a good feel for what color compare mode is and
what it might be used for. Color compare mode isn’t particularly easy to
understand, but it’s not that complicated in actual operation, and it’s
I hope I've given you a good feel for what color compare mode is and
what it might be used for. Color compare mode isn't particularly easy to
understand, but it's not that complicated in actual operation, and it's
certainly useful at times; take some time to study the sample code and
perform a few experiments of your own, and you may well find useful
applications for color compare mode in your graphics code.
A final note: The Read Map register has no effect in read mode 1, and
the Color Compare and Color Don’t Care registers have no effect either
the Color Compare and Color Don't Care registers have no effect either
in read mode 0 or when writing to VGA memory. And with that, by gosh,
we’re actually done with the basics of accessing VGA memory!
we're actually done with the basics of accessing VGA memory!
Not to worry—that still leaves us a slew of interesting VGA topics,
including smooth panning and scrolling, the split screen, color
selection, page flipping, and Mode X. And that’s not to mention actual
uses to which the VGA’s hardware can be put, including lines, circles,
polygons, and my personal favorite, animation. We’ve covered a lot of
challenging and rewarding ground—and we’ve only just begun.
selection, page flipping, and Mode X. And that's not to mention actual
uses to which the VGA's hardware can be put, including lines, circles,
polygons, and my personal favorite, animation. We've covered a lot of
challenging and rewarding ground—and we've only just begun.
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