EPT 462/4 – Mechatronics
Laboratory Module
EXPERIMENT 2
INTRODUCTION TO MICROCONTROLLER
OBJECTIVE:
1. To understand the required input signal and expected output signal of
microcontroller.
2. To understand the functionality of input and output ports of microcontroller.
3. To expose the student basic of microcontroller programming.
INTRODUCTION
Micro-controller (also MCU or µC) is a functional computer system-on-a-chip. It contains
a processor core, memory, and programmable input/output peripherals. Microcontrollers
include an integrated CPU, memory (a small amount of RAM, program memory, or both)
and peripherals capable of input and output. It emphasizes high integration, in contrast to
a microprocessor which only contains a CPU (the kind used in a PC). In addition to the
usual arithmetic and logic elements of a general purpose microprocessor, the
microcontroller integrates additional elements such as read-write memory for data
storage, read-only memory for program storage, Flash memory for permanent data
storage, peripherals, and input/output interfaces.
Microcontrollers are used in automatically controlled products and devices, such as
automobile engine control systems, remote controls, office machines, appliances, power
tools, and toys. By reducing the size, cost, and power consumption compared to a
design using a separate microprocessor, memory, and input/output devices,
microcontrollers make it economical to electronically control many more processes.
(Wikipedia, 2008)
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EPT 462/4 – Mechatronics
Laboratory Module
Assembly language
Microcontrollers were originally programmed only in assembly language, but various
high-level programming languages are now also in common use to target
microcontrollers. These languages are either designed specially for the purpose, or
versions of general purpose languages such as the C programming language. Compilers
for general purpose languages will typically have some restrictions as well as
enhancements to better support the unique characteristics of microcontrollers. Some
microcontrollers have environments to aid developing certain types of applications.
Microcontroller vendors often make tools freely available to make it easier to adopt their
hardware.
An assembly language is a low-level language for programming computers. It
implements a symbolic representation of the numeric machine codes and other
constants needed to program a particular CPU architecture. This representation is
usually defined by the hardware manufacturer, and is based on abbreviations (called
mnemonics) that help the programmer remember individual instructions, registers, etc.
An assembly language is thus specific to certain physical or virtual computer architecture
(as opposed to most high-level languages, which are usually portable).
Instructions (statements) in assembly language are generally very simple, unlike those in
high-level languages. Each instruction typically consists of an operation or opcode plus
zero or more operands. Most instructions refer to a single value, or a pair of values.
Generally, an opcode is a symbolic name for a single executable machine language
instruction. Operands can be either immediate (typically one byte values, coded in the
instruction itself) or the addresses of data located elsewhere in storage. This is
determined by the underlying processor architecture: the assembler merely reflects how
this architecture works. (Wikipedia, 2008)
COMPONENTS AND EQUIPMENTS:
1.
2.
3.
4.
5.
6.
7.
8.
AT89S52 Microcontroller Board
Power Supply
Jumper wire
Breadboard
LED – 8 pcs
RS232 Cable
Computer
Screw driver
PROCEDURE:
Sample program 1 – Blink LED
Connect one LED to Port P2.0 and write the following program and program to your
AT89S52 board.
CPU “8051.TBL”
INCL “8051.INC”
ORG 0000H
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EPT 462/4 – Mechatronics
REPEAT:
LOOP1:
LOOP:
LOOP1:
LOOP:
Laboratory Module
SETB P2.0
MOV R0, #255
MOV R1, #255
DJNZ R1, LOOP
DJNZ R0, LOOP1
CLR P2.0
MOV R0, #255
MOV R1, #255
DJNZ R1, LOOP
DJNZ R0, LOOP1
JMP REPEAT
Sample program 2 – use of subroutine
CPU “8051.TBL”
INCL “8051.INC”
ORG 0000H
REPEAT:
SETB P2.0
CALL DELAY
CLR P2.0
CALL DELAY
JMP REPEAT
DELAY:
LOOP1:
LOOP:
MOV R0, #255
MOV R1, #255
DJNZ R1, LOOP
DJNZ R0, LOOP1
RET
END
Sample program 3 – Blink LED when switch is ON (logic 1) and STOP blinking
when switch is OFF (logic 0). Use of CPL bit and JNB instructions.
Connections: LED - Port P2.0
Switch - Port P1.0.
CPU “8051.TBL”
INCL “8051.INC”
WAIT:
REPEAT:
DELAY:
LOOP1:
LOOP:
ORG 0000H
JNB P1.0, WAIT
CPL P2.0
CALL DELAY
JMP REPEAT
MOV R0, #255
MOV R1, #255
DJNZ R1, LOOP
DJNZ R0, LOOP1
RET
END
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EPT 462/4 – Mechatronics
Laboratory Module
Sample program 4 – Simple input and output operation
Connections: 4 LED
4-bit switches -
P2.0 – P2.3
P1.0 – P1.3
Write the following program and program to your AT89S52 board.
CPU “8051.TBL”
INCL “8051.INC”
START:
ORG 0000H
MOV A, P1
MOV P2, A
JMP START
END
;Read data from 4-bit switches
;Display to LED
Sample program 5 – LED start blinking when the pushbutton switch is pressed. The
values of the 4-bit switches will determine how many times the LED should blink.
Connections: LED
Pushbutton 4-bit switches -
P2.0
P3.0
P1.0 – P1.3
Write the following program and program to your AT89S52 board.
CPU “8051.TBL”
INCL “8051.INC”
WAIT:
REPEAT:
DELAY:
LOOP1:
LOOP:
ORG 0000H
JNB P3.0, WAIT
MOV A, P1
ANL A, #00001111B
MOV B, A
SETB P2.0
CALL DELAY
CLR P2.0
CALL DELAY
DJNZ B, REPEAT
JMP WAIT
MOV R0, #255
MOV R1, #255
DJNZ R1, LOOP
DJNZ R0, LOOP1
RET
END
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EPT 462/4 – Mechatronics
Laboratory Module
Name : _____________________________________
Date : _______________
Matrix No. : ___________________
1. Using eight LED and one switch, write a program to design a simple running light
system. The following table shows the operation of the system.
Switch
OFF (Logic “0”)
ON (Logic “1”)
LED‘s
STOP running
START running
2. Figure 1 illustrates a pedestrian crossing system. The state diagram shows the flow
of the process to control the main traffic light and the pedestrian traffic light. Use LED
for the traffic light. Write a program in assembly language to control the system.
PB = 0
R2
G2
Pedestrian
Traffic Light
Pushbutton (PB)
R1
Y1
G1
G1
R2
15 sec
20 sec
Y1
R2
R1
G2
Main Traffic
Light
5 sec
Figure 1
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PB = 1
EPT 462/4 – Mechatronics
Laboratory Module
DISCUSSION:
CONCLUSION:
REFERENCES
1. Wikipedia. The Free Encyclopedia. Retrieved at: http://en.wikipedia.org/wiki/
Microcontroller. 2008
2. Abdul Rahman Mohd. Saad. Skill Development Course on MICROCONTROLLER
SYSTEMS. 2008
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