LZ: Blank Memory Backup

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LZ: Blank Memory Backup

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To those who want to HELP,


I have pasted together a text file that is a map of a blank backup. I =
cleared my memory, and sent a backup to the computer, then hex viewed =
it. What I want to know is:


Has this been done before?
Do you have any additions (your name will be added to the file)?
Is this map useless, and a waste of time?
Is is helpful?
Would you use it?


I am sorta new, and I just want to contribute. If this is a bad idea, =
please tell me by word (not by flame). BTW, any ideas for a ZShell math =
program (High School level)? Formulas to include? Any ideas in general? =
Thanx.


jyuschak@i21.com


 
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******************************************************************
*                TEXAS INSTRUMENTS 85 CALCULATOR                 *
*                          MEMORY MAP                            *
*                                                                *
*                         JOHN YUSCHAK                           *
******************************************************************


This file is a result of my undertaking to understand the memory 
of the TI-85. I have analyized and re-analyized the TI-85 backups,
and have found out where things are. Most things I still do not 
yet understand, but please bear with me. Also, I would like to 
thank David Boozer, for his knowledge of variables.


******************
*** Memory Map ***
******************


Offset      Purpose or Desription
---------   --------------------------------
0000-0034   File header
0035-08b0   ???
08b1-08ce   Custom menu text
08cf-0914   ???
0915-091b   Ans variable
091c-0924   yStat variable
0925-092d   xStat variable
092e-092f   Checksum






*******************
*** File Header ***
*******************


The backup file header contains information on what date the 
was created, and what time. The file header usually looks like 
this:


  **TI85**   Backup file dated XX/XX/XX, XX:XX


Where X is replaced with the needed information. This information 
is not useful to the user, only if he/she needs to know when the 
last backup was made.






************************
*** Custom Menu Text ***
************************


The offsets 08b1-08ce contain the text of which make up the custom
menu. Every 2 bytes make up one menu. For instance, the offsets 
08b1 and 08b2 make up the first custom menu. These bytes can be 
rearranged (in groups of 2), in effect, moving the contents of 
each menu. 






**********************
*** Variable Bytes ***
**********************


The variable bytes are arranged in a special format recognized by 
the TI-85. For example purposes, we will use the Ans variable. 
Here are the bytes for Ans:


       73 6e 41 03 8b fb 00
       --------------------
  Byte 1  2  3  4  5  6  7


Here is the format of those bytes:


  Byte(s)    Purpose or Description
  -------    -------------------------------------------------
  1,2,3      Contains the name of the variable backwards
  4          Contains the # of characters in the variable name
  5,6        Contains the address of the variable in memory
  7          Contains the type of the variable


  Note: This table does not hold for all variables, since  
        all variable names are not 3 bytes in length.


This file will not go any more in-depth with topic. For a more 
detailed look at variables and related, pick up "Hacking the 
TI-85 Calculator" by David Boozer. His file includes the above 
table, and more in-depth information.


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