Information updated on 9/6/98.

Here is detailed information about the TI-92 Plus built-in assembly support:

ASM (.9XZ) program format

The following is the format of the TI-Graph Link ASM program variables used by the TI-92 Plus.

Offset  Size  Description
0x0     0x8   "**TI92P*" signature
0x8     0x2   01 00
0xA     0x8   Folder name
0x12    0x28  File description text (Must be all zeros? See below)
0x3A    0x6   01 00 52 00 00 00
0x40    0x8   File name
0x48    0x4   File type (0x21)
0x4C    0x4   File size (entire file)
0x50    0x6   A5 5A 00 00 00 00
0x56    0x2   ASM program size (from 0x58 on not including checksum)
0x58    n     ASM program
?       0x1   Signature byte -- MUST BE 0xF3
?       0x2   Checksum from 0x56 on

Some files do not appear to send properly in TI-Graph Link when a file description exists. Fill the description area with zero bytes to avoid this problem.

At the end of the ASM program, just before the 0xF3 signature, there is a relocation table. It is stored in this format:

Low address:   Terminating marker (0x0000 word)
               Destination offset #n (word)
               Referencing offset #n (word)
               Destination offset #n-1 (word)
               Referencing offset #n-1 (word)
               ...
               Destination offset #2 (word)
               Referencing offset #2 (word)
               Destination offset #1 (word)
High address:  Referencing offset #1 (word)

(Thanks to David Ellsworth for the relocation info)

The referencing offset points to the longword which needs to be relocated. The destination offset is the offset the longword is supposed to point at. All offsets are relative to the beginning of the ASM program code.

Execution starts at the first word of the program variable (address 0x58 in the .9XZ file).

ROM calls

TI uses a table of ROM addresses to allow ASM programs to run on all versions. This table is pointed to by RAM address $C8. The following macro will call a ROM function using the number listed below:

ROM_CALL macro
  move.l ($C8),a5
  add.l #\1*4,a5
  move.l (a5),a5
  jsr (a5)
  endm

To call sprintf, for example, you could write:

  ROM_CALL $53

Here is the current list: (a * by the number means that this call is untested)

ST_eraseHelp            0E3
ST_showHelp             0E6
HeapFree                097
HeapAlloc               090
ER_catch                154
ER_success              155
reset_link              24C
flush_link              24D
tx_free                 252*
transmit                250
receive                 24F*
HeapFreeIndir           098
ST_busy                 0E2
ER_throwVar             153
HeapRealloc             09D
sprintf                 053
DrawStrXY               1A9
FontSetSys              18F
DrawTo                  19C*
MoveTo                  19D*
PortSet                 1A2*
PortRestore             1A3*
WinActivate             001*
WinClose                00B*
WinOpen                 01E*
WinStrXY                026*
MenuPopup               03B*
MenuBegin               036*
MenuOn                  03A*
HeapAllocThrow          093
strcmp                  271
FontGetSys              18E
strlen                  27E
strncmp                 272*
strncpy                 26D
strcat                  26E
strchr                  274*
ERD_dialog              151
memset                  27C*
memcmp                  270*
memcpy                  26A*
memmove                 26B*
_du32u32                2AA*
_ds32s32                2A8*
_du16u16                2A6*
_ds16u16                2A4*
_ru32u32                2AB*
_rs32s32                2A9*
_ru16u16                2A7*
_rs16u16                2A5*
DerefSym                079

The DrawCharXY function, at least the one that Fargo used, is not in the ROM table. A replacement is in UTIL.H.

Handle Table

The handle table is at $88FC. The is a pointer to the table at $7592.

To dereference a handle, use this macro:

DEREF macro
  lsl.w #2,\1
  move.l #$88fc,\2
  move.l 0(\2,\1.w),\2
  endm

Handles and Folders (Thanks to Marc Padellini for this info)

The names and handles of all folders is stored in handle number 8. The format of this and the format of the folders themselves is as follows:

Offset  Size  Description
0x0     0x2   Max # of files/folders before handle has to be resized
0x2     0x2   Number of files/folders in table (N)
0x4     0xE*N List of files/folders (each entry is 0xE bytes)
 +0x0   0x8   File/folder name (null padded)
 +0x8   0x2   Null padding for name
 +0xA   0x2   File/folder flags
               Bit 3 - Locked
               Bit 7 - Folder
               Bit 9 - Archived
 +0xC   0x2   Handle of file/folder

Auto Power Down and Timers (Thanks to Joshua Stephanoff for this info)

The timer table is as follows:

Timer N initial value (long):  $5B08+8*N
Timer N value (long):          $5B0C+8*N
Timer N flag (word):           $5B40+2*N

Timer 1 is the Auto Power Down timer and has a default initial value of $1770, which, at 20 Hz, is equivilent of five minutes.

Other Information

The LCD memory starts at $4C00

The following is a table of the locations of the keyboard variables:

Fargo name             New address  Description
tios::kb_globals+$1c   $75BC        Key pressed flag
tios::kb_globals+$1e   $759A        getKey code of last key pressed
tios::kb_globals+$c    $75A2
tios::kb_globals-$6    $75BE

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