ECE 109-001 Program 2: score.asm

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ECE 109-001 Program 2: score.asm

For this assignment, you will write a program that draws 1 – 4 characters on the PennSim’s graphic
display. As this scoreboard is for an engineering school, the program user will be able to accept hex
values 0 – F as individual characters from the user and display them on the graphics screen.
The learning objectives for this assignment are:
 Use load and store instructions to manipulate the content of memory.
 Use I/O routines to allow a user to interact with the program.
Program Specification
The program must start at address x3000.
The program will start by copying clearing the graphics screen.
The program will prompt the user to enter from 1 – 4 hex characters from 0 – F. We can assume wellbehaved users who will only enter lower-case letter for the upper hex characters. The program will
ignore invalid characters as in Program 1. All entered characters shall be immediately echoed to the
console.
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When the user enters 1-3 characters and then the ENTER key, the program will assume they are done. If
they enter 4 characters the program does not wait for the ENTER key. The program only displays the
number of characters entered, no more or less.
The program converts these entered characters into the 7-segment codes shown below and displays them
on the graphics screen in the color red.
When the characters are displayed, the program goes back and prompts for another set of characters. The
screen is not cleared, the next entry shall overwrite the characters on the graphics screen. Therefore the
program must write all of the dark segments as well as the lit segments.
At any time if the lower-case ‘q’ character is pressed on the keyboard the program will print a “Thank
you for playing – Go [Wolfpack/Bulldogs/Seahawks]!" message on the console and HALT.
 Digits a - f

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Coordinates for the 7-segment characters on the graphics displays.
For each of characters 2, 3, and 4 add 25 to the x coordinates.

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Pennsim Graphics
The PennSim graphics display (the “screen”) is 128 by 124 pixels. We use an (x, y) coordinate system
to describe a location on the screen. Location (0, 0) is the top left corner. The x coordinate increases as
we move to the right, and the y coordinate increases as we move down. In other words, (1, 0) is one
pixel to the right of (0, 0), and location (0, 1) is one pixel below (0, 0). Location (127, 123) is the
bottom right corner of the screen.
Details
The PennSim graphics display is bit-mapped, meaning that each pixel has a corresponding memory
location. The content of that memory location controls the color of the pixel.
Pixel Addresses
Addresses xC000 through xFDFF are assigned to the graphics display. The low address corresponds to
the top left corner (0, 0). Moving one pixel to the right adds one to the address, and it “wraps around” to
the next row when it gets to the right edge. Since the display is 128 pixels wide, this means that moving
down one pixel is equivalent to adding 128 to the address.
The address of point (x, y) can be calculated as: xC000 + x + 128y.
For this assignment, you will not need to calculate arbitrary pixel addresses, except to figure out where
the initial location is. You will be moving left (-4), right (+4), up (-512) or down (+512) from the
current address.
You will, however, need to recognize when the Cow is at an edge of the display, so that you don’t go
beyond the edge.
xDF40
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Pixel Color
As mentioned above, the value of the pixel address determines the color of the pixel. The 16 bits
contain 5 bits for each RGB component of color: bits [14:10] for red, [9:5] for green, and [4:0] for blue.
Bit 15 is ignored. The higher value of a component, the more of that color is present. The table below
gives the color values (in hex) needed for this program.
Color Value
Red x7C00
Green x03E0
Blue x001F
Yellow x7FED
White x7FFF
Black x0000
Miscellaneous
For more explanation about the PennSim display, see the PennSim Reference Manual.
The ASCII code for the Return key is x0A (#10). This is listed as linefeed (LF) in the ASCII table.
Hints and Suggestions
 As always, design before you code! Draw a flowchart to organize and document your thinking
before you start writing the program.
 Work incrementally! For example, implement one command at a time. Make sure the program
works before moving on to the next command. This way, you always have working code.
 It’s not a bad idea to submit each working version of your program to Moodle. Then, if your
machine crashes (it happens!), you haven’t lost everything. Each time you submit, it overwrites the
previous submission, so you can submit as many times as you like. But don’t expect that we can
recover some previous version of your code if you accidentally clobber it. (You should have some
sort of backup system for your schoolwork, right?)
 Test your program with a wide variety of inputs.
 Use the PennSim simulator and assembler. There are other simulators and assemblers out there, but
there are some differences. Your program will be graded using PennSim, and no other tools will be
used or considered. You must use the provided p3os.obj and p3os.sym files for the operating
system.
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Administrative Info
Any corrections or clarifications to this program spec will be posted on the Discussion Forum. It is
important that you read these postings, so that your program will match the updated specification. (I
recommend strongly that you subscribe to the forum, so that you will not miss any updates or
corrections.)
What to turn in:
 Submit your one-page flow chart to Moodle on-time
 Assembly Language Source file – it must be named score.asm. Submit via Moodle to the
Program 2 assignment.
The program will be graded by one of the TAs, and your grade will be posted in the Moodle
gradebook. You will also get back some information about what you got wrong, and how points
were deducted (if any).
DO NOT submit .obj or .sym files. Do not submit a .txt file, a .doc file, or anything like that. It
must be a simple text file with the proper .asm extension. If we are unable to open or interpret
your file, you will get a zero for the assignment (even if it has the right name!).
Grading criteria:
 5 points: Submission of Flow Chart on schedule.
 5 points: Correct type of file, submitted with the proper name. (No partial credit!! These are
essentially FREE POINTS! Don’t screw it up.)
15 points: Program is complete and assembles with no warnings and no errors using the PennSim
assembler. To be “complete,” there must be code that makes a reasonable attempt to meet
the program specs. Programs that do not assemble will not be graded any further. (For
warnings, points will be deducted, but the program will be tested for correctness.)
10 points: Proper coding style, comments, and header. Use indentation to easily distinguish labels
from opcodes. Leave whitespace between sections of code. Include useful comments and
meaningful labels to make your code more readable. Your file must include a header
(comments) that includes your name and a description of the program. Don’t cut-and-paste
the description from the program spec – that’s plagiarism. Describe the program in your own
words. This category is somewhat subjective, but the goal is that your program should be
easy to read and to understand.

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65 points: The program handles all commands correctly:
 (5 points) clears the screen and prompts the user correctly.
 (10 points) Reads the keyboard characters, echoing, ignoring invalid characters, etc
 (5 points) Accepts between 1 and 4 characters.
 (15 points) Displays each character 0-9 correctly on the graphics screen.
(15 points) Displays each hex character A - F correctly on the graphics screen.
(10 points) Holds the graphics content until the next entry cleanly writes over the previous.
(5 points) Quit.