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Assembly Programming on the TI-89PowerPoint Presentation

Assembly Programming on the TI-89

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- 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

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

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.

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.

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.

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.

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.

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

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

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

Resources

- Motorola 68k Family Programmer's Reference
- http://www.freescale.com/files/archives/doc/ref_manual/M68000PRM.pdf

- Techno-Plaza's TIGCC Assembly Lessons
- http://www.technoplaza.net/assembly/

- Virtual TI Emulator
- http://www.technoplaza.net/downloads/download.php?program=67

- Ticalc.org
- http://www.ticalc.org/

- TI-89/TI-92 Plus Developer's Guide
- http://education.ti.com/downloads/pdf/us/sdk8992pguide.pdf

- The Official TIGCC Site
- http://tigcc.ticalc.org/

- TI-89 Graphing Calculator Product Center
- http://education.ti.com/us/product/tech/89/features/features.html

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