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Real Time Clock using ATMega16
Description
The ATMega16 chip has a real-time counter that operates
asynchronously when a 32,768hz
watch crystal is connected to it, providing a real-time clock.
The watch crystal needs to connect
to pins TOSC1(pin 28) and TOSC2(pin 29).
Hardware requirements
ATMega16
32,768 KHz crystal
LCD display
>> the following software (using codevision avr compiler )
uses timer 2 CTC compare match
and ther are three switches used to adjust seconds,minutes and
hours.
>> timer 2 use prescalar 1024 and the OCR value will be 32
or (20 hex).
code sample
#include
// Alphanumeric LCD Module functions
#asm
.equ __lcd_port=0x1b ;PORTA
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#endasm
#include
char s=0,m=0,h=0;
char t,u;
// Timer 2 output compare interrupt service routine
interrupt [TIM2_COMP] void timer2_comp_isr(void)
{
// Place your code here
s=s+1;
if (s==60)
{
s=0;
m=m+1;
if (m==60)
{
m=0;
h=h+1;
if (h==24)
{
h=0;
}
}
}
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}
// External Interrupt 1 service routine
interrupt [2] void int0(void)
{
s=s+1;
if(s==60)
{
s=0;
}
}
interrupt [3] void int1(void)
{
m=m+1;
if(m==60)
{
m=0;
}
}
interrupt[19] void int2(void)
{
h=h+1;
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if(h==24)
{
h=0;
}
}
///////////////////////////////
char tenth(char a)
{
t=a/10;
return t;
}
//////////////////////////////
//////////////////////////////
char unit(char b)
{
t=b/10;
u=b-t*10;
return u;
}
////////////////////////////////
// Declare your global variables here
void main(void)
{
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// Timer/Counter 2 initialization
// Clock source: TOSC1 pin
// Clock value: PCK2/1024
// Mode: CTC top=OCR2
// OC2 output: Disconnected
ASSR=0x08;
TCCR2=0x0F;
TCNT2=0x00;
OCR2=0x20;
// LCD module initialization
lcd_init(16);
TIFR|=0x80;
// Global enable interrupts
#asm("sei")
while (1)
{
// Place your code here
lcd_gotoxy(0,0);
t=tenth(h);
lcd_putchar(t+0x30);
u=unit(h);
lcd_putchar(u+0x30);
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lcd_putsf(":");
t=tenth(m);
lcd_putchar(t+0x30);
u=unit(m);
lcd_putchar(u+0x30);
lcd_putsf(":");
t=tenth(s);
lcd_putchar(t+0x30);
u=unit(s);
lcd_putchar(u+0x30);
};
}
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proteus simulation
>>>> here is a link containing the project avr and
its proteus simulation
http://www.mediafire.com/?w03l55v308dd95e
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