CSC 230 Assignment 3

CSC 230 Assignment 3
This assignment has three parts:
1) Programming Pre-submission: A subset of the complete program needs to be
submitted via the Assignments link on the Connex site on or before March 11 well
before 11:55.
2) Programming Submission: The final program will be submitted via the Assignments link
on the Connex site on or before March 18 well before 11:55. The main submission file
should be in a file called display.asm; the extended work should be in a file called
display_ext.asm.
3) Demonstration: You will be required to demonstrate the functioning of the
programming part of your assignment to a member of the teaching team. Demos will
occur the week of March 20-24 in the labs.
Objectives
 Gain confidence with assembly language programming.
 Create effective subroutines/functions.
 Use peripherals: the LCD
 Become familiar with the use of busy-waiting
 Become familiar with the use of interrupts
Academic Integrity
Prior to submitting your assignment, carefully read the University policy on Academic Integrity:
http://web.uvic.ca/calendar2014/FACS/UnIn/UARe/PoAcI.html
If you do not understand the meaning of anything in the document, please ask. A plagiarism
detection tool will be used on assignment submissions.
Assignment 3 Description
Please note for all programing assignments, you must include your name and student number
and edit the documentation appropriately. Make sure the submitted work is yours and not
someone else. The directions below describe
The LCD
The boards we are using have a Hitachi HD44780 compatible LCD display that has its own
(simple) processor. To communicate with that processor a specific protocol is used that
initializes and controls the LCD screen. Learn more about how the LCD controller works by
looking at the data sheet: https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
A previous CSC 230 student has written a library of subroutines for this assignment. The table
below lists the subroutines, their parameters and what they do.
There is an example program, that shows how to use the LCD functions in the file:
lcd_example.asm. Review both files carefully until you are able to understand their
functionality. While doing that, search for a way to set the number of rows on the LCD to 2 and
the number of columns to 20.
LCD Moving Message Sign
LCD advertising signs often move written messages on a screen and flash. The movement and
the flashing are very effective at attracting attention. The goal of this programming task will be
to display alternately two written messages, gradually moving them down and across the
screen, and to display and flash both messages. Please name this file as “display.asm” for
submission on connex.
In particular, the program will need to:
a. Create two messages that will be displayed on the screen. For example, assume:
msg1 = "YourName"
msg2 = "UVIC: Computer Sci"
b. Using the messages (msg1 and msg2) create another two messages that contain the
same characters, but in reverse order. Using the above example messages, the
messages, called msg3 and msg4, would be:
msg3 = "emaNruoY"
msg4 = "icS retupmoC :CIVU"
c. When the program starts, the LCD screen will contain both: msg1 in the first row of the
screen and msg2 in the second row both of which start in the first column.
d. After approximately one second, the LCD screen will be cleared then will be set to
contain: msg2 on the first line of the screen, starting in the second column, and msg3
on the second line of the screen, also starting in the second column.
e. After approximately one second, the LCD screen will be cleared then will be set to
contain: msg3 on the first line of the screen, starting in the first column, and msg4 on
the second line of the screen, also starting in the first column.
f. After approximately one second, the LCD screen will be cleared then will be set to
contain: msg4 on the first line of the screen, starting in the second column, and msg1
on the second line of the screen, also starting in the second column.
g. <continue here
h. After approximately two seconds, clear the screen, then repeat all of the above steps 2
more times.
i. Finally, clear the screen, then set the screen to flash (alternate between) the screen
totally full of the character ‘*’ and the screen totally full of the character ‘.’.
Implementation Help
The instructor's solution has the following in the data segment:
; sample strings
; These are in program memory
msg1_p: .db "YourName", 0
msg2_p: .db "UVIC: Computer Sci”, 0
.dseg
;
; The program copies the strings from program memory
; into data memory.
;
msg1: .byte 200
msg2: .byte 200
; These strings contain the 18 characters to be displayed on the LCD
; Each time through, the 18 characters are copied into these memory locations
line1: .byte 19
line2: .byte 19
line3: .byte 19
line4: .byte 19
With these data definitions, the main loop of the application looks like:
initialize the lcd
clear the lcd
copy the strings from program to data memory
do 3 times:
set row counter to 0 and column counter to 0
display line1
set row counter to 1
display line2
delay 1 second
set row counter to 0 and column counter to 1
display line2
set row counter to 1
display line3
delay 1 second
set row counter to 0 and column counter to 0
display line3
set row counter to 1
display line4
delay 1 second
set row counter to 0 and column counter to 1
display line4
set row counter to 1
display line1
delay 2 seconds
do many times:
clear the lcd
display all *
delay 1 second
display all .
delay 1 second

clear the lcd
You should make extensive use of subroutines in your code. In fact, each line above is its own
subroutine. Including the delay code (which you can borrow from your lab) the solution is ~300
lines of assembly language. Start now!
Extending the Moving Message Sign
Now, add some features. Here are some options. You can choose any one of them.
 Implement a scrolling display for longer messages: Scroll them across the screen,
wrapping such that a character that falls off one end will appear on the other.
 Extend the application so that you can press the “UP” button will display only messages
1 and 2 while pressing the “DOWN” button will display only message 3 and 4.
 Add another improvement, here are some suggestions:
o Allow button presses to increase and decrease the sign change speed
o Allow the user to select different messages
 Please name this file as “display_extended.asm” for submission on connex.
In order to handle button presses gracefully you will have to do something other than busy loop
waiting, either by checking the buttons in your delay subroutine or by using timer interrupts.