Re: LZ: screen and graphics memory
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Mr Chan Kheong Sann wrote:
>
> In the file 85hack.txt by David Boozer and in the ti-ram.txt by Dan Eble and
> Rob Taylor, the locations $8641 and $80DF are shown as the Graphics and Text
> memory addresses. However when I write information to those locations
> directly, nothing shows up on the screen.
The reason why nothing shows up on the screen is because you didn't use
the ROM_CALL(D_ZT_STR) or any of the other ROM_CALL's for puting text on
the screen. when you wrote information to $8641 and $80DF you just
stored information in those memory locations.
> Later in ti-ram.txt, it states $FC00 as the real bitmapped memory or something
> like that and indeed, writing bytes to $FC00 causes corresponding bit-mapped
> patterns to appear on the screen when the TI is set to graphics mode.
> So what are $8641 and $80DF, what are they used for? And where is the location
> of the real screen memory? ie: does there exist a location in memory that if
> I ld it with a number, the ascii eqivelant will immediately show up on the
> screen?
As i said before $8641 and $80DF are used for storing information. In
regular TI mode, $8641 is used for the graph screen and $80DF is used
for the text screen.
>
> It seems that often memory at $80DD onwards is used to store variable
> data in a program, but there is a warning in the Zshell Function Library that
> calling certain functions may wipe out or alter the contents of these memory
> locations. So are these something like memory locations which are
> copied to the screen memory? Also, I don't understand why we choose to store
> our variables in text memory when that might be where we want to put our text.
> Surly there must exist better places in memory to store our variables.
storing varibles to text memory does not affect what is put onto the
screen because while in ZShell the only memory that directly updates the
screen is the video memory($FC00).
>
> If ld a,$4
> out (5),a
>
> puts the TI85 into graphics mode, how do we put it back into text mode again?
While in graph mode you can still put text on the screen and store
information to text memory. BTW ZShell puts the 85 back into text mode
after you leave a program.
>
> Thanks
>
> Kheong.
> cks@ee.vlsi.nus.sg
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PCoMP
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