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From: Phil_Bowers.henr801E@XEROX.COM
Newsgroups: comp.sys.apple
Subject: Page Flipping.
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Date: 22 Mar 89 20:32:24 GMT
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I have noticed that the Double Hi-Res screen has two pages,
but I don't see a soft switch to flip between the two.
Does anyone know if Double Hi-Res page flipping is possible, and
if it is how does one go about implementing it.

                Thanks,
                        Bob


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  I have just come onto the mailing service and I and not sure what type
Apple (breed, whatever) you have. I have an Apple II+. There are two Hi-Res
screen buffers; one from $2000 to $3FFF (page 1)and the second from $4000
to $5FFF(page 2). 
   I have some code in both BASIC and Assembler that allows you to write to
one page while looking at the other, and then flip to the one just written
(via a peek, or an Assembler load instruction). To set up  variuos sreen
combinations, all graphics or graphics/text, only four soft switches  are
used, and only one is needed to READ from in order to flip the screens but
I do not know them off-hand) If this would be of help, let know and I will
figure how to get the info to you with the least fat-finger errors. sent
your mail note to:      
                       Phil Bowers:henr801e:xerox
LATER;
I found this info in my desk. The addresses  of the soft-switches come in
pairs;
 set 1     $C050 graphics ,                    or $C051 text
 set 2     $C052 all text or graphic ,  or $C053 mix text and  graphics
 set 3    $C056 lo-res graphic  ,        or $C057 hi-res
 set 4     $C054 page 1 ,                     or $C057 page 2
this is also in table #5 of one of your manuals.(after the Assembler
instrucrtion code section) you have to reference each of these addresses
the first time to set the proper screen. Once this is done, you can flip
between page 1 and 2 by  referering (by a READ type statement) to one of
the last two addresses.  These  should be used in this order even though
the manual shows them in a different order.

          phil