rtc.c

一个LCD驱动程序

//*****************************************************************************
//
//  File........: RTC.c
//
//  Author(s)...: ATMEL Norway
//
//  Target(s)...: ATmega169
//
//  Compiler....: IAR EWAAVR 2.27b
//
//  Description.: Real Time Clock (RTC)
//
//  Revisions...: 1.0
//
//  YYYYMMDD - VER. - COMMENT                                       - SIGN.
//
//  20021015 - 1.0  - Created                                       - LHM
//
//*****************************************************************************

//  Include files
#include "Main.h"
#include "RTC.h"

// Lookup table used to determine the highest date in a specific month
unsigned char MaxDate[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; 

/******************************************************************************
*
*   Function name:  Start_Timer2
*
*   returns:        none
*
*   parameters:     none
*
*   Purpose:        Start Timer/Counter2 in asynchronous operation using a 
*                   32.768kHz crystal.
*
*******************************************************************************/
void RTC_init(void)
{
    Delay(1000);            // wait for 1 sec to let the Xtal stabilize after a power-on, 
   
    __disable_interrupt();  // disabel global interrupt
    
    TIMSK2 = 0;             // disable OCIE2A and TOIE2

    ASSR = (1<<AS2);        // select asynchronous operation of Timer2
    
    TCNT2 = 0;              // clear TCNT2A
    TCCR2A = (1<<CS22) | (1<<CS20);             // select precaler: 32.768 kHz / 128 = 1 sec between each overflow
    
    while((ASSR & 0x01) | (ASSR & 0x04));       // wait for TCN2UB and TCR2UB to be cleared
    
    TIFR2 = 0xFF;           // clear interrupt-flags
    TIMSK2 = (1<<TOIE2);    // enable Timer2 overflow interrupt
    
    __enable_interrupt();                 // enable global interrupt
    
    // initial time and date setting
    HOUR = 8;
    MINUTE = 0;
    SECOND = 0;
    DAY = 4;
    MONTH = 11;
    YEAR_LO = 2;
    YEAR_HI = 20;
}

/******************************************************************************
*
*   Function name:  Time_update
*
*   returns:        None
*
*   parameters:     None
*
*   Purpose:        Updates the time and date variables
*
*******************************************************************************/
void Time_update(void)
{
   unsigned char LeapYear = FALSE;
    
    //the variable SECOND gets updated in the Timer0 Overflow Interrupt Routine every second 
      
    if(SECOND > 59)                         // if one minute
    {   
        SECOND = 0;                         // clear SECOND
        MINUTE++;                           // increment MINUTE
    
        if(MINUTE > 59)                     // if one hour        
        {
            MINUTE = 0;                     // clear MINUTE
            HOUR++;                         // increment HOUR
            
            if(HOUR > 23)                   // if one hour
            {
                HOUR = 0;                   // clear HOUR
                DAY++;                      // increment DAY
                
                if(MONTH == 2)              // if it's February
                {
                    // check for leap year
                    if(!YEAR_LO)                        // if YEAR_LO = 0, (a century has passed)
                    {
                        if(!(YEAR_HI%4))                // check if YEAR_HI is divisible by 4 
                            LeapYear = TRUE;                // then it is a leap year
                    }
                    else if(!(YEAR_LO%4) & (YEAR_LO != 0))  // else if YEAR_LO is divisible by 4 and not zero
                        LeapYear = TRUE;                    // then it's a leap year
                }                        
                
                if(DAY > (MaxDate[MONTH] + LeapYear))   // if a whole month has passed
                {
                    DAY = 1;                // clear DAY
                    MONTH++;                // increment MONTH
                        
                    if(MONTH > 12)          // if one year
                    {   
                        MONTH = 1;          // clear MONTH
                        YEAR_LO++;          // increment YEAR_LO
                        
                        if(YEAR_LO > 99)    // if one century
                        {
                            YEAR_LO = 0;    // clear YEAR_LO
                            YEAR_HI++;      // increment YEAR_HI
                                
                            if(YEAR_HI > 99)    // if 100 centuries
                                YEAR_HI = 0;    // the AVR is still going strong :)
                        }
                    }    
                }
            }
        }
    }  
}


/******************************************************************************
*
*   Timer/Counter2 Overflow Interrupt Routine
*
*   Purpose: Increment the varible SECOND by one.
*
*******************************************************************************/
#pragma vector = TIMER2_OVF_vect
__interrupt void TIMER2_OVF_interrupt(void)
{
    SECOND++;               // increment second
}