FUCULTY OF ENGINEERING AND TECHNOLOGY
LAB 01
MODULE: ADVANCED DIGITAL SYSTEM DESIGN
CODE: CTEN 511
LAB TITLE: MPLAB INTRODUCTION
NAME: KARABO DAVIS BOGAISANG
STUDENT ID: 14001009
PROGRAM: BENG COMPUTER AND TELECOMMUNICATIONS
Abstract
The purpose of this lab was to introduce the environment of MPLAB X IDE and assembly language
through some simple examples of programming using the PIC24 family. Addition and subtraction were
used as examples for programming in this lab.
Introduction
MPLAB X IDE is comprehensive software that has editing, project management and design in it. It
used in development of embedded system application using microcontroller Microchip PIC. Assembly
language is a language that used for programming microcontroller. Before programming, these
assembly language instructions into microcontroller memory, it has to convert to machine language so
that microcontroller easily understands. This conversion is done by software called assembler in
MPLAB X.
Objectives
•
•
To use MPLAB X to simulate the PIC24 assembly language program in the mptst_word project
to become familiar with the MPLAB X environment
Do simple programming tasks using PIC24 assembly language
Apparatus
• MAPLAB X
Procedure
Task 1
Open the mptst_word project, and build all to assemble the project. Open the program memory to view
program memory and file registers. Open watch window then add u16_i, u16_j,u16_k and WREG0,
WREG1, WREG2. Using the simulator to single step the program, both the memory locations and
watched locations observed as the instructions are being executed.
Modify the value of i=2047 to i=1009. Building and simulating the program, the values watch contents
and file register contents were observed.
Task 2 : myadd
Copy the project mptst_word and name the copy myadd. Few editing is done to make the program to
add a four digit hexa number to another four digit hexa number. Reserving space for u16_lsp, u16_msp
and u16_sum. Then the code for adding the two numbers was added as it will be shown in the code for
myadd. Watch contents and file register contents were observed and the outcome is displayed in the
results section.
code for myadd
;
; Just check out MPLAB
.include "p24Fxxxx.inc"
.global __reset
;The label for the first line of code.
.bss
;unitialized data section
;;These start at location 0x0800 because 0-0x07FF reserved for SFRs
u16_lsp:
.space 2
;Allocating space (in bytes) to variable.
u16_msp:
.space 2
;Allocating space (in bytes) to variable.
u16_sum:
.space 2
;Allocating space (in bytes) to variable.
;..............................................................................
;Code Section in Program Memory
;..............................................................................
.text
;Start of Code section
__reset:
; first instruction located at __reset label
mov #__SP_init, w15
;Initalize the Stack Pointer
mov #__SPLIM_init,W0
mov W0, SPLIM
;Initialize the stack limit register
;__SP_init set by linker to be after allocated data
;User Code starts here.
; C Program equivalent
; #define avalue 1009
; #define bvalue 1400
; uint16 lsp,msp,sum;
;
;
.equ avalue,0x3F1 ;1009
.equ bvalue,0x578 ;1400
;u16_lsp = avalue; /* myvalue = 1009 */
mov #avalue, W0
; w0 = 1009 (w0 is wreg)
mov wreg,u16_lsp
; i = 1009 (W0 is wreg)
;u16_msp = bvalue; /* myvalue = 1400 */
mov #bvalue, W0
;w0 = 1400
mov wreg,u16_msp
;u16_msp=1400
; u16_sum = u16_lsp + u16_msp
mov u16_lsp,wreg
; w0 = u16_lsp
add u16_msp,wreg
; w0 = w0+u16_msp
mov wreg,u16_sum
; u16_sum = 0
done:
goto
.end
done ;Place holder for last line of executed code
;End of program code in this file
Task 3: mysub
Project named mysub is created by applying almost the same procedure from task 2. For this particular
one was to add and subtract a two digit hexa decimal number. Reservation of SFRs and adding the code
for addition and subtraction is shown in the code for mysub. Outcome is displayed in the results
section.
code for mysub
;
; Just check out MPLAB
.include "p24Fxxxx.inc"
.global __reset
;The label for the first line of code.
.bss
;unitialized data section
;;These start at location 0x0800 because 0-0x07FF reserved for SFRs
u8_i:
.space 2
;Allocating space (in bytes) to variable.
u8_j:
.space 2
;Allocating space (in bytes) to variable.
u8_k:
.space 2
;Allocating space (in bytes) to variable.
u8_l:
.space 2
;Allocating space (in bytes) to variable.
u8_m:
.space 2
;Allocating space (in bytes) to variable.
;..............................................................................
;Code Section in Program Memory
;..............................................................................
.text
;Start of Code section
__reset:
; first instruction located at __reset label
mov #__SP_init, w15
;Initalize the Stack Pointer
mov #__SPLIM_init,W0
mov W0, SPLIM
;Initialize the stack limit register
;__SP_init set by linker to be after allocated data
;User Code starts here.
; C Program equivalent
; #define avalue 2047
; uint16 u8_i,u8_j,u8_k,u8_l,u8_m;
;
; i = avalue; /* myvalue = 2047 (0x7FF) */
; i = i + 1; /* i++, i = 2048 (0x800) */
; j = i;
/* j is 2048 (0x0800) */
; j = j - 1; /* j--, j is 2047 */
; k = j + i; /* k = 4095 (0x0FFF) */
;
.equ avalue, 0x9 ;9
.equ bvalue, 0xA ;10
.equ cvalue, 0x1E ;30
;u8_i = avalue; /* myvalue = 09 */
mov #avalue, w0
; w0 = 09 (w0 is wreg)
mov wreg,u8_i
; u8_i = 09
;u8_j = avalue; /* myvalue = 10 */
mov #bvalue, w0 ;wreg = 10
mov wreg, u8_j
;u8_j = 10
;u8_k = avalue; /* myvalue = 10 */
mov #cvalue, w0 ;wreg = 30
mov wreg, u8_k
;u8_k = 30
; u8_l = u8_i + u8_j
mov u8_i,wreg
add u8_j,wreg
mov wreg,u8_l
; w0 = u8_i
; w0 = w0+u8_j
; u8_l = 0
; u8_m = u8_k - u8_l
mov u8_l,wreg
sub u8_k,wreg
mov wreg,u8_m
; w0 = u8_l
; wreg = u8_k - w0
; u8_m = 0
done:
goto done ;Place holder for last line of executed code
;End of program code in this file
.end
Results
Task 1
View of program memory
View of file register
Values of watches being observed
Values of file registers being observed
watch contents for i = 1009
file register contents for i =1009
watch contents for myadd
file register contents for myadd
watch contents for my sub
file register contents for mysub
Analysis
Table showing convertion from hexa decimal to decimal and otherwise.
HEXADECIMAL 0
DECIMAL
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
A
10
B
11
C
12
D
13
E
14
F
15
To convert from decimal to hexa decimal, the value is divided by 16 until getting 0 as the result, and
the value of the hexa decimal is read from remainders starting from the bottom.
DIVISION
RESULT
REMAINDER (in HEX)
1009/ 16
63
1
63 / 16
3
15
3 / 16
0
3
Answer taking reminders from the bottom
3151 but 15 =F in hexadecimal
Answer =(3F1)hex
Converting back to decimal, the values are multiplied by 16 considering the bit where the are.
For (3F1)hex
considering F =15
(3*16**2+15*16**1+1*16**0) = 1009
Converting 578 to decimal
(5*16**2+7*16**1+8*16**0) = 1400
Converting 1E
E = 14
(1*16**1+14*16**0) = 30
Converting 13 to decimal
(1*16**1+3*16**0) = 19
Discussion
It is quite a challenge to differiate between data address and the actual data. Having to move the value
from data address where it is stored to a temporary storage for the case where watches were used for
the purpose of arithmetic. Then move the result to the address to were it is stored, it is quite an
experience and a good way to learn the language and its opearation.
Conclusion
The Objective of this lab we clearly meet, the intern was to introduce the environment of MPLABX.
Doing some simple programming to get fimiliar with the coding of the environment in which it is
assembly language. The two exercises given for adding and subtracting hexa decimal numbers is quite
a good example for introduction of assembly language.
REFERENCES
[1] T. Wilmshurst, Designing Enbedded Systems withPIC Microcontrollers, Principles and
Applications, Second Edition, Newnes, 2009
[2] R. Arunthavanathan, MPLAB programming, Research gate, 23 November 2017