In this presentation we can learn about basic concept of Timer, types of timer, timer0, features, and prescaler - frequency divider clearly.

1. MICROCONTROLLER BASED SYSTEM DESIGN
“TIMER 0 CONCEPT”
V.KALAIRAJAN M.E;
ASSISTANT PROFESSOR,
ELECTRICALAND ELECTRONICS ENGINEERING
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY,TRICHY
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY TIMER 0 CONCEPT 1

2. “TIMER 0 CONCEPT”
VIEWS:
 TIMER.
 TYPES OF TIMER.
 TIMER0 MODULE.
 PRESCALER - FREQUENCY DIVIDER.
 THE STRUCTURE OF THE OPTION_REG REGISTER.
 BLOCK DIAGRAM OF THE TIMER0 MODULE.
 PIC TIMER0 FORMULA FOR INTERNAL CLOCK.
 PIC TIMER0 FORMULA FOR EXTERNAL CLOCK.
 PROGRAM FOR DELAY OF 1 SEC USING TIMER0.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY TIMER 0 CONCEPT 2

3. “TIMER 0 CONCEPT”
TIMER:
 Now a days, we plan and build systems that perform various
processes that depend on time.
 Simple example of this process is the digital wristwatch. The role
of this electronic system is to display time in a very precise
manner and change the display every second (for seconds), every
minute (for minutes) and so on.
 To perform the steps we've listed, the system must use a timer,
which needs to be very accurate in order to take necessary actions.
The clock is actually a core of any electronic system.
 Each module can generate an interrupt to indicate that an event has
occurred (i.e. timer overflow). The timer modules are:
 Timer0 Module
 Timer1 Module
 Timer2 Module
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4. “TIMER 0 CONCEPT”
TIMER0 MODULE:
 The Timer0 module timer/counter has the following features:
 8-bit timer/counter
 Readable and writable
 8-bit software programmable prescaler
 Internal or external clock select
 Interrupt on overflow from FFh to 00h
 Edge select for external clock
PRESCALER - FREQUENCY DIVIDER:
 We can use Prescaler for further division of the system clock. The
options are:
1:2, 4, 8, 16, 32, 64, 128, 256
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5. “TIMER 0 CONCEPT”
THE STRUCTURE OF THE OPTION_REG REGISTER:
 We perform all the necessary settings with OPTION_REG Register. The
size of the register is 8 bits.
INITIALIZING THE OPTION_REG REGISTER:
The following is an example how we can initialize the OPTION_REG:
PSA=0; // Prescaler is assigned to the Timer0 module
PS0=1; // Prescaler rate bits
PS1=1; // are set to “111”
PS2=1; // which means divide by 256
TOSE=0; // rising edge
TOCS=0; // Internal instruction cycle clock
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6. PIC16CXX PIPELINING
BLOCK DIAGRAM OF THE TIMER0 MODULE.
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7. “TIMER 0 CONCEPT”
 Timer mode is selected by clearing bit T0CS (OPTION<5>).
In timer mode, the Timer0 module will increment every
instruction cycle (without prescaler).
 If the TMR0 register is written, the increment is inhibited for
the following two instruction cycles.
 The user can work around this by writing an adjusted value
to the TMR0 register. Counter mode is selected by setting bit
T0CS (OPTION<5>).
 In counter mode, Timer0 will increment either on every
rising or falling edge of pin RA4/T0CKI.
 The incrementing edge is determined by the Timer0 Source
Edge Select bit T0SE (OPTION<4>). Clearing bit T0SE
selects the rising edge. Restrictions on the external clock
input
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8. “TIMER 0 CONCEPT”
PIC TIMER0 formula for internal clock:
PIC TIMER0 formula for external clock:
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9. “TIMER 0 CONCEPT”
Program for Delay of 1 sec using Timer0:
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10. “TIMER 0 CONCEPT”
CONCLUSION:
 In this above presentation we can learn about basic concept of
Timer, types of timer, timer0, features, prescaler - frequency
divider clearly.
REFERENCES:
 Mazidi, M.A.,“PIC Microcontroller” Rollin Mckinlay, Danny
causey Printice Hall of India, 2007.
 Ravichandran,C., and Arulaalan,M., “Microcontroller Based
System Design”, Suchitra Publications, Ist edition,2016.
 Dr.Balamurugan.C.R., Periyaazhagar., “Microcontroller Based
System Design”, Megnus Publications, Ist edition,2016.
 Online wikipedia search.
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