1. CENTRE OF DIPLOMA STUDIES
COMPUTER ADDED DESIGN LABORATORY
LABORATORY INSTRUCTION SHEET
DEK 3133
Subject Code and Name
MICROCONTROLLER
Experiment Code 03
Introduction to functions, conditions and
Experiment Title Hardware Timer using TMR0
Course Code DET/DEE/DEX

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Amendment Date 27/7/2010
SUBJECT INFORMATION
SUBJECT : DEK 3133 MICROCONTROLLER
TOPIC : Lab 3 – Introduction to functions, conditions and Hardware Timer using TMR0
AIM : Learn the further programming technique using C language
1 OBJECTIVES
1.1 To understand the concept of programming in C using functions and conditions
1.2 To learn how to use TMR0 as a hardware timer
2 EQUIPMENT
2.1 PIC Development Board – PICDEV
2.2 MPLAB IDE Program
2.3 Mikro C
2.4 Proteus
2.5 The PIC Development Board User manual
2.6 Power supply 9V

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3 THEORY
3.1 Functions
3.2 Conditions
3.3 Using TMR0
The special file register 01, Timer Zero (TMR0), which can be used as a counter or timer which, once
started, run independently of the program execution. This mean it can count inputs or clock pulses

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concurrently with the program. The counter/timer can also be set up to generate an interrupt when it has
reached its maximum value, so that the main program does not have to keep checking it to see if a
particular count has been reached.
3.4 REGISTERS ASSOCIATED WITH TIMER0
• TMR0
o 8 bit TMR0 Module Register
o Count from 0 to 255 (00h to FFh)
• INTCON
o GIE - Global Interrupt Enable bit - controls all possible interrupt sources
simultaneously.
1 - Enables all unmasked interrupts.
0 - Disables all interrupts.
o T0IE - TMR0 Overflow Interrupt Enable bit controls interrupt enabled by TMR0 overflow.
1 - Enables the TMR0 interrupt.
0 - Disables the TMR0 interrupt.
o T0IF - TMR0 Overflow Interrupt Flag bit registers the timer TMR0 register overflow, when
counting starts from zero.
1 - TMR0 register has overflowed (bit must be cleared in software).
0 - TMR0 register has not overflowed.

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• OPTION
o TOCS – Clock Select bit (Bit 5)
1 – Pulses are brought to TMR0 timer/counter input through the RA4 pin
0 – Internal cycle clock (Fosc/4)
o TOSE – Source Edge Select bit (Bit 4)
1 – Increment on high to low transition on TMR0 pin
0 – increment on low to high transition on TMR0 pin
o PSA – Prescaler Assignment bit (Bit 3)
1 – Prescaler is assigned to the WDT
0 – Prescaler is assigned to the TMR0 timer/counter
o PS2 (Bit 2), PS1(Bit 1), PS0 (Bit 0) – Prescaler Rate Select bit
PS2 PS1 PS0 TMR0 WDT
0 0 0 1:2 1:1
0 0 1 1:4 1:2
0 1 0 1:8 1:4
0 1 1 1:16 1:8
1 0 0 1:32 1:16
1 0 1 1:64 1:32
1 1 0 1:128 1:64
1 1 1 1:256 1:128
Prepared By: Approved by:
Signature : Signature:
Name: Mohamad Bin Md. Som Name: Shamsul B. Mohamad
Date: 27 July 2010 Date: 27 July 2010

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4 ATTENTION
4.1 Do not move any IC or device inside the board without any order from your instructor.
5 EXPERIMENT PROCEDURE
5.1 Functions and Conditions
5.1.1 Base on the circuit below (circuit 1), key in the given C code and simulate it using
Proteus. Write your observations.
Circuit 1

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#define BUTTON1 PORTA.F0
#define BUTTON2 PORTA.F1
#define BUTTON3 PORTA.F2
#define BUTTON4 PORTA.F3
void pattern1(void) //function for pattern 1
{
PORTB = 0b11111111;
}
void pattern2(void) //function for pattern 2
{
PORTB = 0b10101010;
}
void pattern3(void) //function for pattern 3
{
PORTB = 0b11110000;
}
void pattern4(void) //function for pattern 4
{
PORTB = 0b00001111;
}
void main(void)
{
ADCON1 = 0b00000110; //Set ADCON1 for Port A as a digital input
TRISA = 0b11111111; //Port A as input port
TRISB = 0b00000000; //Port B as output port
PORTB = 0b00000000; //Clear PORTB at start up
while(1) //endless loop
{
if (BUTTON1 == 1) //Test button at PORTA bit 0 if pressed.
pattern1(); //call function pattern1
else if (BUTTON2 == 1)
pattern2(); //call function pattern2
else if (BUTTON3 == 1)
pattern3(); //call function pattern3
else if (BUTTON4 == 1)
pattern4(); //call function pattern4
else
PORTB = 0b00000000; //All LED off if no button pressed
} //end of while (endless loop)
}//end of main func
5.2 Assignment 1.
Base on the Circuit 1, Modify the C code so that each button have a different pattern of animated LEDs. Use 1
second delay for each changing pattern. Test your result in Proteus and put your modifying code in the report.

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5.3 Using TMR0 as a Hardware Timer
Circuit 2
5.3.1 Base on the figure above (Circuit 2), the PIC use 4Mhz for its clock speed. Write the
program to blink the LED every one second by using TMR0. The code is shown below.
#define LED1 PORTB.F0
#define TOCS OPTION_REG.F5
#define TOSE OPTION_REG.F4
#define PSA OPTION_REG.F3
#define PS2 OPTION_REG.F2
#define PS1 OPTION_REG.F1
#define PS0 OPTION_REG.F0
#define GIE INTCON.F7
#define TMR0IE INTCON.F5
#define TMR0IF INTCON.F2
//Public Variable
unsigned int overflow;
void interrupt(void) //Interrupt subroutine
{
if (TMR0IE == 1 && TMR0IF == 1) //TMR0 made interrupt

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{
overflow++;
TMR0IF = 0; //clear interrupt flag
TMR0IE = 0; //Disable TMR0 interrupt
if (overflow == 15) //TMR0 is overflow about 15 times ~~ 1 second.
{
LED1 = ~LED1;
overflow = 0; //reset overflow to 0
}
TMR0IE = 1; //enable TMR0 interrupt
TMR0 = 0; //restart TMR0 value to 0
}
}
void main(void)
{
overflow = 0;
//port setup
TRISB = 0; //port B is output
PORTB = 0; //initial value for PORTB is 0
//TMR0 setup
TOCS = 0; //Internal cycle clock (Fosc/4)
PSA = 0; //Prescaler is assinged to the TMR0 timer
PS2 = 1;
PS1 = 1;
PS0 = 1; //Prescaler rate is selected to 1:256
TMR0 = 0; //Initial value for TMR0 is 0
//Interrupt Setup
GIE = 1; //Enable all interrupt
TMR0IE = 1; //Enable the TMR0 interrupt
while(1); //infinite loop
}
5.3.2 Burn the *.hex file into PIC and test the PIC at the development board. Write your
observation in the report.
5.4 Assignment 2
5.4.1 Write a C program so that the LED is blinking using hardware delay which is blinking
every 1 second. Assume PIC clock speed is 1MHz and prescaler used is 1:256. Simulate
your result using Proteus.

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6 REPORT PREPARATION AND SCHEMA.
(1) 2 persons for 1 report.
(2) Due date to send report is 1 weeks after lab date.
(3) Report schema following below requirements:
• Lab report cover sheet for 1st page.
• Objective, theory, equipments for the 2nd page. (5) (5M)
• Observations. (20)
1. Observations from 5.1.1 (Proteus Simulation) (10 M)
2. Observations from 5.3.2 (TMR0 run on development board) (10 M )
• Result. (35)
1. Assignment 1 source code & Flow Chart ( 15 M )
2. Assignment 2 source code & Proteus Simulation ( 20 M )
• Discussion. (25)
1. List the Registers related to TMR0 and describes the procedure to setup the TMR0 (15M)
2. If the PIC is supplied with 1 MHz clock speed, calculate time taken for TMR0 to
overflow. Assume that a prescaler 1:256 is used. Show the calculation in your report
(10 M)
• Conclusions. (15)