Assembly Programming on the TI89

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Assembly Programming on the TI-89

• Created By
• Adrian Anderson Trevor Swanson

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TI-89 Calculator

• Released in 1998 as a more portable version of
  the TI-92, which was much larger and had a QWERTY
  keyboard.
• Evaluates and performs algebraic expressions
• Performs calculus functions
• Can graph in several coordinate systems,
  including 3D
• Has pretty print, meaning it draws algebraic
  expressions (such as radicals and exponents) in a
  mathematical way

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Assembly vs. TI-Basic

• TI-Basic is simpler, but more restricted
• - Quick access to high-level features
• - Many ROM functions cannot be called from
  TI-Basic
• - Strict rules when calling other procedures
• - Must use the graph screen for pixel work
  in TI-Basic
• Assembly is much faster
• Assembly programs cannot be edited on the
  calculator

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Motorola 68K Processor

• Sixteen 32-bit registers and one 16-bit Condition
  Code Register (CCR)
• The first 8 registers are data registers which
  can hold values associated with the assembly
  program
• The next 8 are address registers which can serve
  as software stack pointers, index registers, or
  base address registers. The eighth of the
  address registers is the user stack pointer, a
  register which always holds the top value of the
  system stack
• The final register, the 16-bit CCR, holds the
  conditions of the information from the most
  recent operation. These include carry, overflow,
  extend, zero, and negative.

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Motorola 68K Processor
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Assembly Length Modifiers

• Adding .b to the end of an instruction will
  make the instruction move data in bytes
• Adding ".w" to the end of an instruction will
  cause the processor to treat the arguments as
  words.
• Adding ".l" to the end of an instruction will
  treat the arguments as long words (32 bits).
• Example move.w 1,-(a7)    .
  Pushes the number 1 to the stack as a
  word.

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Assembly Commands

• Movement Instructions
• move Moves the data from one address to another
  
• movem Moves data from multiple locations to
  adjacent memory locations
• clr Clears the contents of a register.
• lea Loads an address to a register.
• pea Pushes data to the stack.
• Arithmetic Instructions
• add Adds the source to the destination, and
  places it in destination.
• addx Like add, but adds 1 if the extend flag is
  set.
• sub Subtracts the source from the destination,
  and places the result in the destination
• neg Subtracts the data in the address from 0.
• cmp Subtracts the source from the destination,
  but does not store the result. Used to change the
  CCR.
• muls.w Multiplies the source by the
  destination, and places the result in the
  destination.
• divs.w Divides the destination by the source,
  and places the result in the destination.

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Branch Instructions

• bra Sets the Program Counter (PC) ahead by a
  number of bytes equal to the argument.
• b(cc) Sets the PC forward by a number of bytes
  equal to the argument if a certain condition is
  set.
• Condition Tests
• cs - True if the Carry bit is set
• cc - True if the Carry bit is cleared
• eq - "Equal to Zero" - True if the Zero bit is
  set
• ne - "Not Equal to Zero" - True if the Zero bit
  is cleared
• vs - True if the Overflow bit is set
• vc - True if the Overflow bit is cleared
• mi - "Minus" - True if the Negative bit is set
• pl - "Plus" - True if the Negative bit is cleared
  
• ge - "Greater than or Equal to Zero" - True if
  the Negative and Overflow are both cleared, or if
  they are both set.
• lt - "Less than or Equal to Zero" - True if the
  Negative bit is set and the Overflow bit is
  cleared, or vice versa.
• gt - "Greater than Zero" - As ge, but the Zero
  bit must also be cleared.
• le - "Less than Zero" - As lt, but true if the
  Zero bit is set, regardless of the other
  conditions.

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Rotate and Shift Instructions

• asl "Arithmetic Shift Left" - Moves the Most
  Significant Bit (MSB) into the Carry bit in the
  CCR, shifts each bit to the left, and inserts a 0
  into the Least Significant Bit (LSB).
• lsl Works exactly as asl.
• asr Moves the LSB into the Carry bit in the
  CCR, shifts each bit to the right, and inserts a
  copy of the old MSB to the new MSB.
• lsr As asl, but places a zero in the MSB.
• rol Shifts each bit to the left, moves the MSB
  to the Carry flag in the CCR, and moves the Carry
  flag into the LSB.
• roxl As rol, but the Carry flag is then copied
  to the Extend bit.
• ror Shifts each bit to the right, moves the LSB
  to the Carry flag in the CCR, and moves the Carry
  flag into the MSB.
• roxr As ror, but the Carry flag is then copied
  to the Extend bit.
• swap Exchanges the high word in the specified
  register with the low word.

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Binary Logic

• not Flips all bits in the destination
• and Performs a bitwise AND (destination bit is
  true only if both input bits are true) of the two
  values, and places the result in the destination
• andi As and, but the source is a constant
• or Performs a bitwise OR (destination bit is
  true if either source bit is true) of the two
  values, and places the result in the destination
• ori As or, but the source is a constant
• eor Performs a bitwise exclusive OR
  (destination bit is true of one source bit is
  true and one is false) of the two values, and
  places the result in the destination
• eori As eor, but the source is a constant

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A Sample Program

• Bounce.89z
• A small ball continuously bounces off of the
  edges of the screen
• Program flow
• Initialize variables and clear screen
• Runs a loop to slow the program down
• Check for keyboard press
• Switch directions if ball hits a wall
• Erase the ball
• Moves the ball in the correct direction
• Draws the ball

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Advanced Techniques

• Masking
• A mask determines which bits will be
  set and which will not be set
• Often uses and to erase unwanted bits
• Jumptable
• List of the locations of certain functions in
  memory
• All functions can be called by addresses

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Declarations
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Saving the Screen
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Initializing
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Loops and Direction Testing
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Direction Testing 2
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Moving and Clearing
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Moving and Clearing 2
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Moving Image
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Drawing Image
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Drawing Image 2
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Cleanup
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Resources

• Motorola 68k Family Programmer's Reference
• http//www.freescale.com/files/archives/doc/ref_ma
  nual/M68000PRM.pdf
• Techno-Plaza's TIGCC Assembly Lessons
• http//www.technoplaza.net/assembly/
• Virtual TI Emulator
• http//www.technoplaza.net/downloads/download.php?
  program67
• Ticalc.org
• http//www.ticalc.org/
• TI-89/TI-92 Plus Developer's Guide
• http//education.ti.com/downloads/pdf/us/sdk8992pg
  uide.pdf
• The Official TIGCC Site
• http//tigcc.ticalc.org/
• TI-89 Graphing Calculator Product Center

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Black Slide