// Use writec() and timer interrupt functions to implement a digital clock!
// By using the timer interrupt, users can easily implement any timing functions needed.
// To improve the accuracy of the clock, writings to LCD should be minimized.
// Proved to work on MT-20, MT-28 and MT-ARM chips, need to remove the "seconds" display for MT-40 series chips!

int   ps; // previous seconds
int   s;  // seconds
int   h;  // hours
int   m;  // minutes

main()
{
    
   h = 23; m = 59; s = 50; 
     
   writes("~XCEOL", 0);			// disable the 'clear to end of line' feature of LCD 
   update_hours();
   writec(2, ':', 0);                   // show separator
   update_minutes();
   writec(5, ':', 0);                   // show separator
   loop {
     if(s != ps) { ps = s; update_seconds(); }
     if(s >= 60) { s = 0; m++; update_minutes(); }
     if(m >= 60) { m = 0; h++; if(h >= 24) h = 0; update_minutes(); update_hours(); }
   }
}

second_tick() timer 1000
// this timer interrupt increments the 'seconds' counter every 1000ms, i.e. 1 second
// do keep the toal processing time for this function small to maintain the accuracy of the timing required.  
{
   s++;
}

update_seconds()
{
   writec(6, s/10+'0', 0);
   writec(7, s%10+'0', 0);
}

update_minutes()
{
   writec(3, m/10+'0', 0);
   writec(4, m%10+'0', 0);
}

update_hours()
{
   writec(0, h/10+'0', 0);
   writec(1, h%10+'0', 0);
}