LZ: screen and graphics memory

Subject: LZ: screen and graphics memory
From: Mr Chan Kheong Sann <cks@vlsi.ee.nus.sg>
Date: Sat, 12 Oct 1996 12:16:29 +0800 (SST)
In-Reply-To: <>

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. 
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?


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.


If ld a,$4
   out (5),a


puts the TI85 into graphics mode, how do we put it back into text mode again?


Thanks


Kheong.
cks@ee.vlsi.nus.sg