Re: Tandy 1000 graphics page register documentation?

On Apr 24, 10:00 am, Jim Leonard <MobyGa...@xxxxxxxxx> wrote:
Does anyone have an explanation or example source code
that explains using the page register to have more than one video
page?

Thankfully, I was able to obtain the original Tandy 1000 reference
manual, which has more concise documentation in this area than the
1000 TX manual. (Why the later manuals would have LESS information is
beyond me.) It turns out that the page register at 03DFh takes the
following format:

76543210
xxmmmddd

....where mmm is the memory page that is mapped to B800h, and ddd is
the memory page that is currently displayed by the adapter. The page
register can take different values for both, which is awesome -- it
means that the video adapter can be displaying, for example, page 7
while you work on page 6 in 160x200x16 mode, all via the same B800h
window.

The "xx" above claims to be necessary for some memory configuration
regarding alpha or graphics modes, but ignoring it (setting both bits
to 0) didn't seem to affect anything so that's how I'm using it.
.

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