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INTRODUCTION
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The 68000 processor keeps a 256(d) byte exception vector table at the bottom
of memory (address $000000). This table contains pointers to 64(d) vectors;
each vector is an absolute pointer to a specific location in memory. Most of
these vectors point to routines, although some have other functions. Each
vector is referred to with an index between 0(d) to 63(d) inclusive.

The vectors are assigned as follows:

Address in table   Assigned function
----------------   -----------------
0000 to 0007       Reset vector (initial SSP and PC)  (0-1)
0008 to 000B       Bus error vector                     (2)
000C to 000F       Address error vector                 (3)
0010 to 0013       Illegal instruction vector           (4)
0014 to 0017       Zero divide vector                   (5)
0018 to 001B       CHK instruction vector               (6)
001C to 001F       TRAPV instruction vector             (7)
0020 to 0023       Privilege violation vector           (8)
0024 to 0027       Trace vector                         (9)
0028 to 002F       Line 1010/1111 emulator vectors  (10-11)
0030 to 003B       Unassigned, reserved             (12-14)
003C to 003F       Uninitialised interrupt vector      (15)
0040 to 005F       Unassigned, reserved             (16-23)
0060 to 0063       Spurious interrupt vector           (24)
0064 to 007F       Level 1-7 interrupt auto-vectors (25-31)
0080 to 00BF       TRAP #0-15 instruction vectors   (32-47)
00C0 to 00FF       Unassigned, reserved             (48-63)
0100 to 03FF       User interrupt vectors          (64-255)

Some of these vectors are triggered when an error is encountered by the
68000 processor. Others can be triggered directly by a TRAP instruction.
The interrupt auto-vectors, or auto-ints, are triggered when a specific
hardware event occurs.

Note: Any RAM addresses found here apply only to ROM 1.2 through 1.12.

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VECTORS USED BY THE TI-92
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Line 1010 emulator
------------------
  Opcode $Axxx: Trigger error {xxx}, with identical numbering to that used
  in the (TIOS) variable "errornum". Note that there are some error numbers
  that are undocumented in Appendix B of the TI-92 manual.

Line 1111 emulator
------------------
  Print "Line 1111 Emulator" and freeze. Unused.

Auto-Int 1
----------
  Triggered every 4th time [600017] is incremented. It runs at
  approximately 350 Hz. See Ports.txt.

Auto-Int 2
----------
  Triggered periodically while key(s) other than [ON] are held down. The
  rate depends both on battery strength and on which key(s) are being held
  down, and is usually in the ballpark of about 600 Hz.

Auto-Int 3
----------
  Print "Level 3 Autovector" and freeze. Never triggered.

Auto-Int 4
----------
  Link Service

Auto-Int 5
----------
  Triggered when [600017] is set to its initial value. After ROM
  initialization, it runs at approximately 18 Hz. See Ports.txt.

Auto-Int 6
----------
  Triggered when [ON] is pressed.

Auto-Int 7
----------
  Protected memory violation. Triggered when memory below [$000120] is
  written while bit 2 of [$600001] is set.

Trap 0
------
  JSR ($40xxxx + D0.W)

  D0.W  Subroutine
  ----- ----------
  $01A2 [60001A] = $FF, [05342] = $00
  $01B8 flush word buffer, set size to 1 word (push *buffer)
  $01E4 [05510] = $00000000, [0550C] = $00000000, JMP $400100 (reset)
  $01F0 print error string and freeze (push *string)

Trap 1
------
  Change Interrupt Mask

  Input : D0.W = new interrupt mask (bits 10,9,8 of new SR)
  Output: D0.L = old SR

Trap 2
------
  Reset Calculator

  Input : nothing
  Output: calculator is reset

Trap 3
------
  ?

Trap 4
------
  Turn Off, Turn On (see also Auto-Int 6)

  Input : nothing
  Output: calculator turns off, waits for [ON]

Trap 5
------
  ? same as trap 7

Trap 6
------
  ?

Trap 7
------
  ? same as trap 5

Trap 8
------
  ?

Trap 9
------
  A0.L = $4004F8 + 4 * D0.W

  Input : D0.W = {00...11}
  Output: A0.L = $4004F8 + 4 * D0.W
	  D0.L = 4 * D0.W;

  D0  pointer to
  --  ----------
  00       (ROM)  ?contrast_up()
  01       (ROM)  WinOpen()
  02       (ROM)  ?reset_link()
  03  (RAM)       2 structures
  04       (ROM)  ?contrast
  05       (ROM)  WinStr()
  06  (RAM)       ?key_buffer
  07       (ROM)  flush word buffer, set size to 1 word (push *buffer)
  08       (ROM)  table for isupper(), etc.
  09       (ROM)  ?contrast_up()
  0A       (ROM)  ?contrast_down()
  0B       (ROM)  [60001A] = $FF, [05342] = $00
  0C       (ROM)  getkey() table
  0D       (ROM)  ?
  0E  (RAM)       LCD memory
  0F       (ROM)  Boolean ?read_word_buffer(WORD *a, BUFFER *b)
  10       (ROM)  RAM test
  11       (ROM)  WinMoveTo()

TRAP 10
-------
  Enter self test

TRAP 11
-------
  Print "Trap 11" and Freeze

TRAP 12
-------
  Print "Trap 12" and Freeze

TRAP 13
-------
  Print "Trap 13" and Freeze

TRAP 14
-------
  Print "Trap 14" and Freeze

TRAP 15
-------
  Print "ER_throw" and Freeze