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   Code Snippets    Submitted by alexmd

soft Real Time Clock implementation

● April 25, 2013 ● Coded in C 
typedef struct t_smalltm{
  u16 year;
  u8 mon;
  u8 day;
  u8 hour;
  u8 min;
  u8 sec;
} t_smalltm;

t_smalltm rtc;

//**************************************************************
// call this function every 1 sec. from timer interrupt.
// for fast code execution rtc will be placed in internal RAM.
//**************************************************************
void realTimeClock(void)
 {u8 rest;

  if (++rtc.sec==60)        // sec
   {
    rtc.sec=0;
    if (++rtc.min==60)      // min
     {
      rtc.min=0;
      if (++rtc.hour==24)   // hour
       {
        rtc.hour=0;
        rtc.day++;          // day
        rest=rtc.year%4;
        if ((((rest==0 && rtc.year%100!=0) || rtc.year%400==0)
			      && rtc.mon==2 && rtc.day==30)
           || (rest && rtc.mon==2 && rtc.day==29)
           || ((rtc.mon==4 || rtc.mon==6 || rtc.mon==9 || rtc.mon==11) 
			      && rtc.day==31)
           || (rtc.day==32))
             {
              rtc.day=1;
              if (++rtc.mon==13)   // mon
                rtc.mon=1, rtc.year++; // HAPPY NEW YEAR !  :)
             }
        }
      }
    }
 }
//**************************************************************
// read RTC function
void getRTC(t_smalltm* stm)
 {
  disableInterrupts();     // evite erronated read
                           // because realTimeClock is called from interrupt
  memcpy(stm,&rtc,sizeof(t_smalltm));
  enableInterrupts();
 }
//**************************************************************
// set RTC function
void setRTC(u16 year, u8 mon, u8 day, u8 hour, u8 min, u8 sec)
 {
  disableInterrupts();
  rtc.year=year;
  rtc.mon=mon;
  rtc.day=day;
  rtc.hour=hour;
  rtc.min=min;
  rtc.sec=sec;
  enableInterrupts();
 }