Lab 4 MPLAB Introduction and PIC24 Assembly Language

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ECE383: Microcomputers – Lab 4
MPLAB Introduction and PIC24 Assembly
Language
Goals: The goals of this lab are to introduce students to basic PIC24 assembly language, usage of
the MPLAB Integrated Development Environment (IDE) and associated tools.
1. Introduction
This lab introduces the Microchip MPLAB Integrated Design Environment. All files referenced in the lab are
assumed to be in C:\microchip\chap3. The tasks in this lab are:
• Use MPLAB to simulate the PIC24 assembly language program in the
C:\microchip\chap3\mptst_word.mcp project to become familiar with the MPLAB environment.
• Implement some simple programming tasks using PIC24 assembly language.
This lab requires you to capture portions of the screen. The lab computers use the Windows operating system.
This includes the “Snipping Tool” that may be used to capture portions of the screen. Other third party tools are
also available.
As always, read through the entire lab and scan the supplied files before starting work. The reporting
requirements have you verify computations performed by the assembly language program. In all cases, make it
easy for the TA to verify your computations by showing your work. NOTE: When writing MPLAB assembly
language programs, do not use variable names a or b as these are reserved names. All hand calculations
requested should be shown on a separate piece of paper in the lab report.
2. Pre-lab
For this lab assignment, Task1 and Task 2 should be completed as a pre-lab assignment prior to your assigned
lab time. You may also complete all the tasks (including Task 3 and Task 4) prior to the lab time. This may reduce
your time in the lab, but is not required.
TA check: As soon as you enter lab, provide the TA with a pre-lab report that includes the complete assembly
language programs. Lab time will be devoted to debugging the program execution and correcting any errors
within MPLAB noted by the lab instructor. Make sure your group member names and date are on the pre-lab
report.
3. TASK 1: MPLAB Introduction
Perform the following steps:
• Copy the files in C:\microchip\chap3\ to a suitable directory on your network drive or hard disk. Make
sure the directory you use has no spaces in the directory path. An example of a good directory name to 
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use would be C:\temp\username where “username” is your unique login name.
• Startthe MPLAB IDE. Use Project-Open and open themptst_word.mcp projectlocated in your directory.
• Use Configure-Select Device to select the PIC24HJ128GP502 device for your processor.
• Use Project-Build All (Ctrl+F10) to assemble the program. If the source file is not already open, doubleclick on the mptst_word.ssource file to open it.
• After the project is assembled, use View-Program Memory and open the program memory window.
Scroll the window until you find your program in memory. This should start at location 0x204.
• Use View-File Registers to view data memory. Scroll to location 0x800, which is where your variables
willstart.
• Use View-Special Function Registersto view the special function registers (W0-W15, etc.).
• Open a watch window (View-Watch) and use Add Symbol and Add SFR to watch variable values and
special function register values, respectively, of the i, j, k variables and the W0 (WREG0) special function
register.
• Use Debugger-Select Tool-MPLAB Sim to select the MPLAB Simulator.
• Use Debugger-Step Over (F8) to single step the program. Watch both the memory locations and watch
window locations, and correlate their changing values with the instructions being executed.
TA check: Show the TA the task 1 results including the finalstate of the program, data memory, and the watch
window. Use a screen capture tool to capture these windows and include them in your lab report. Include your
source assembly language program in your lab report.
Modify the avalue equate (statement.equ avalue, 2047)to be the last four digits of yourstudent ID. Reassemble
the program and re-simulate it. Take a screen shot of both the Watch window contents and the memory window
contents. In your report, you must show calculations that verify the screen shot values match the expected
result (note, avalue is in decimal, as are the last four digits of your student ID: the values displayed in the file
registers window are in HEX).
TA check: Show the TA the modified task 1 results including the final state of the program, data memory, and
the watch window. Use a screen capture tool to capture these windows and include them in your lab report.
Include your source assembly language program in your lab report.
4. TASK 2: myadd.s
Use Project-Save Project As and save the mptst_word project as a new project named myadd. Save the
mptst_word.s file as myadd.s. Right-click on the mptst_word.s file in the left-hand workspace window and use
the Remove option to remove it from the myadd project. Right click on the Source Files and use Add Files to add
the myadd.s file to the project. Edit the myadd.s file and remove all of the instructions from
mov #avalue, W0 through mov WREG,k. You can now use this file as a start for a new program.
Your CWID student number is an eight digit number Y7Y6Y5Y4Y3Y2Y1Y0. For this task we will consider this to be
an eight digit hexadecimal number.
Write a program to add the four digit hex number formed by 0xY3Y2Y1Y0 to the four-digit hex number formed by
0xY7Y6Y5Y4. Reserve space for two 16-bit variables in data memory named lsp and msp to hold the hex values
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0xY3Y2Y1Y0 and 0xY7Y6Y5Y4 respectively. Reserve space for a variable named sum to hold the sum of lsp and msp.
The following C code describes the program. You must translate each line of the C program to corresponding
assembly instruction(s).
uint8 aa=100, bb=22;
uint16 lsp, msp, sum;
lsp = 0xY3Y2Y1Y0; // Four digits of CWID treated as hex
msp = 0xY7Y6Y5Y4; // Four digits of CWID treated as hex
sum = lsp + msp;
sum = sum + aa + bb;
Use the watch window to watch variables aa, bb, lsp, msp, and sum. Also, use the data memory window to
monitor the memory locations corresponding to these variables.
TA check: Show the TA the task 2 results including the finalstate of the program, data memory, and the watch
window.Use a screen capture tool to capture these windows and include them in yourlab report. Include your
source assembly language program in your lab report. Since you will be working in teams in the lab, use only
one student number for each team.
5. TASK 3: mysub.s
Create a project named mysub using the same procedure given in Task 2 (Project -Save Project As, etc.)
corresponding assembly language file named mysub.s. Using digits Y5Y4Y3Y2Y1Y0 from your student ID, write
an assembly language program that implements the following C program. You must translate each line of the C
program to assembly instruction(s).
uint16 xx=0xDEAD, yy=0xBEEF;
 uint8 i, j, k, l, m;
i = Y1Y0;
j = Y3Y2;
k = Y5Y4;
l = i + k;
m = j – l;
xx=xx-yy-m;
Variables i, j, k, l, m are all 8-bit (byte) variables and xx and yy are 16-bit variables. Y1Y0, Y3Y2 and Y5Y4 are
considered as decimal numbers for this task. Use the watch window to watch variables i, j, k, l, m, xx, and yy.
Also, use the data memory window to monitor the memory locations corresponding to these variables. Write
your program,simulate it, and verify that you calculate the correct results.
Hint: If you experience the error “Link Error: Cannot access symbol (xx) at an odd address”, initialize 16-bit
variables first and then 8-bit variables. That is, all variables defined using the .space 2 directive should appear
before variables defined using the .space 1 directive.
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Give the value of the flags after the execution of each instruction. Assume that W0 = j and W1 = l.
Instruction Value of flags
C Z OV N
ADD.B W0,W1,W0
SUB.B W0,W1,W0
TA check: Show the TA the task 3 results including the finalstate of the program, data memory, and the watch
window.Use a screen capture tool to capture these windows and include them in yourlab report. Include your
source assembly language program in your lab report.
6. TASK 4: mylogicops.s
Create a project named mylogicops using the same procedure given in Task 2 (Project -Save Project As, etc.)
corresponding assembly language file named mylogicops.s. Write an assembly language program that
implements the following C program. You must translate each line of the C program to assembly instruction(s).
uint8 u8_a, u8_b, u8_c, u8_d, u8_e, u8_f;
uint16 u16_x=0x0001;
u8_a=0xAF;
u8_b=0x50;
u8_c= u8_a & u8_b;
u8_d= u8_a | u8_b;
u8_e= u8_a ^ u8_b;
u8_f=~u8_a;
u16_x=~u8_d | (u16_x & u8_c);
Use the watch window to watch variables u16_x, u8_a, u8_b, u8_c, u8_d, u8_e, and u8_f. Also, use the data
memory window to monitor the memory locations corresponding to these variables. Write your program,
simulate it, and verify that you calculate the correct results.
In addition to simulating your program within MPLAB, you must download your program to your PIC24 hardware (the
Microstick II) and demonstrate the execution of your program on hardware to the TA. Make sure the Microstick II
development board is attached to a USB port on your computer and make sure the slider switch on the board is set
to position A. With the mylogicops project open, use the following steps
• If not already selected, use Configure-Select Device to select the PIC24HJ128GP502 device for your
processor.
• Use Debugger-Select Tool-Starter Kit on Board to select the Microstick II as the target. You should see
messages in the MPLAB Output window indicating a successful connection to the Microstick II board.
• Use Project-Build All (Ctrl+F10) to assemble the program. If the source file is not already open, doubleclick on the mylogicops.ssource file to open it.
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• Use Debugger-Program to download your code to the Microstick II. You should see messages in the
MPLAB Output window indicating successful programming of the Microstick II board.
• After the project is downloaded, use View-Program Memory and open the program memory window.
• Scroll the window until you find your program in memory. This should start at location 0x204.
• Use View-File Registers to view data memory. Scroll to location 0x800, which is where your variables
willstart.
• Use View-Special Function Registersto view the special function registers (W0-W15, etc.).
• Open a watch window (View-Watch) and use Add Symbol and Add SFR to watch variable values and
special function register values,respectively, of the all of the defined variables and the W0 (WREG0)special
function register.
• Set a breakpoint on the first line of your assembly language program by double clicking on the line in the
assembly language program.
• Begin the execution of your program by selecting Debugger-Run.
• Use Debugger-Step Over (F8) to single step the program. Watch both the memory locations and watch
window locations, and correlate their changing values with the instructions being executed.
TA check: Show the TA the task 4 results including the finalstate of the program, data memory, and the watch
window for both the MPLAB PIC24 simulator and the PIC24 hardware. Use a screen capture tool to capture
these windows and include them in your lab report. Include your source assembly language program in your
lab report.
7. Report
At the next lab period, provide the TA a printed copy of the lab report following the ECE383 Lab report Template
given on the class website. Each lab group will submit one joint lab report to the TA. Yourreportshould have the
reporting requirements needed for Tasks 1, 2, 3, and 4. The TA will take off a significant number of points (up
to 15% from total lab grade) if your assembly language source does not have the required comments. The
commentsshould indicate which assembly language source lines implement which C statements.
8. GRADING POLICY
1. Completion of the prelab assignment (20%)
2. Completion of Task 1 with results included in lab report (15%)
3. Completion of Task 2 with results included in lab report (15%)
4. Completion of Task 3 with results included in lab report (15%)
5. Completion of Task 4 with results included in lab report (15%)
6. Completeness, quality, and correctness of the lab report (20%)