I need to know how to specifically access the pixel data in VGA mode
12h (640x480x16) in four continously addressable bit planes at segment
A000H.
Basically, I want the couple of lines of code that will make the first
bitplane apear at A000H so I can copy it out, then switch the bank so
that the second bit
plane appears there, up to the fourth bit plane.
It is important that the entire bitplane show up as 38,400 bytes
starting at A000 so that I can
copy the entire bit plane with a single memcpy(). It is not usefull to
me to have to read individual bytes one at a time- I need the whole
bit plane at A000 all at once.
I'd image this is pretty straghtforward to do and described in any of
the good VGA refernce books that were around 10 years ago. Alas, I no
longer own any of the old
VGA reference books (I got married).
I'd accept ASM code, C code, psueduo code, or even a brief descrition
of the exact steps. Just enough so I'll be able to create a program
that does it.
Note: If you do not understand what I am talking about when I say that
the whole bit plane has to show up as one continuous array of bytes at
A000, please do not answer this question. I already know who to get
the data one byte at a time and this will not work for my application
since I need to copy a full bit plane of data at once using DMA.
Thanks! |
