CS 273

Homework 5

Due Friday, October 26, 2001

No reading assignment this week.

Not From the Book

Background

If you are given a corner and the center of a rectangle, you can compute the other three points of the rectangle. It doesn't matter which corner you are given, the computation is the same. Think about the diagonal across the rectangle that starts at the corner you are given. The center of the rectangle is the midpoint of that line, thus, you can use the midpoint formula and a little algebra to calculate the corner at the other side of the diagonal. Once you have that, the rest is easy. Work it out on paper before you start programming. Also make sure you pay attention to how you use the HC11 registers.

Assignment (30 points)

Write an assembly program to computes the other three corners given one corner and the center point of the rectangle. Your program should:

• Be well-structured. It should be possible to easily break it down into the structures described in the book and class.
• Use rmb to declare variables for the X and Y coordinates for the three corners you are to compute. These should appear in memory locations 00 - 05. At the end of your program, the values must be correct in memory, not just in registers. You can assume that all values are 8-bit positive integer values.
• Use fcb to declare the given data (the one corner and the center) as constants. For example:

  Xcnr1    FCB    2
  Ycnr1    FCB    6
  Xcntr    FCB    7
  Ycntr    FCB    13

  These constants need to start in location $f900.
• Use equ to define symbols for the start of RAM, the start of EEPROM, the start of CONSTS, and the RESET interrupt vector location.
• Explicitly stop your program; use a "dead loop" as defined in class.
• Use appropriate comments to describe what your program is doing. Writing proper comments is an art; you need to describe what your code is doing, not restate the lines of code. So, to look at a likely fragment of code that might turn up in your program, here's a good example of commenting:

  	  
  	  ldaa    Xcnr1  * copy p1 X value
  	  staa    Xcnr2  * ...into p2 X value
  	  
  	  

  and here's a bad example:

  	  
  	  ldaa    Xcnr1  * load Xcnr1 into accumulator a
  	  staa    Xcnr2  * store accumulator a into Xcnr2
  	  
  	  

• The comments at the top of the program should indicate:
  • Who the author is of the program
  • Who you worked with on the program

You may (in fact, you probably will) find it helpful to start by writing the program in some imperative high-level language of your choice, and translate that program into assembly code. But that's not an explicit part of the assignment.

Assemble, simulate, and debug your program before submitting it through the Web Submission page. Note: You will receive no points for a program that does not assemble.

Last modified: Fri Oct 19 22:55:34 MST 2001