Page 446 - Programming Microcontrollers in C

A Clock Program 431

{
inituart(BAUD_RATE); /* initialize the UART */
pit_init(); /* initialize the PIT */
vector(handler,FAST_AUTOVECTOR);
/* put handler address in FAST_AUTOVECTOR. */
Enable_Fast_Interrupts();
FOREVER
{
keep_time(); /* keep track of the time */
if(kbhit())
reset_time();
}
}

void reset_time(void)
{
int c;

c=getch();
switch(c)
{
case ‘m’:
case ‘M’: if(++minutes>MAX_MINUTES)
minutes=0;
break;
case ‘h’:
case ‘H’: if(++hours>MAX_HOURS)
hours=MIN_HOURS;
break;
}
output_time(); /* send out a new time after each change */
}
Listing 8-10: Complete Clock Routine
Note that in this program the only functions that have direct access
to the memory of the computer are those that involve the PIT. The
pit_init() routine is truly chip specific as is the pit_isr().
All of the other routines could be used on just about any computer. It
is always good to place the chip-specific routines in functions by
themselves. Then when you need to change to another chip, all of the
chip-specific code is lumped together and the general-purpose code
is easy to lift and move to the new program.
All #define object-like and function-like macros are placed at
the head of the program. Also, a list of function prototypes is included.