counter + lcd

[nina]

I am trying implement this source code but I did not understand how it work.
I want develop a code that count hours and when reach a certain hour a message will be showed on LCD.

This part of the code never is called by main function and how does it count time?

#int_rtcc // This function is called every time
void clock_isr() { // the RTCC (timer0) overflows (255->0).
// For this program this is apx 76 times
if(--int_count==0) { // per second.
++seconds;
int_count=INTS_PER_SECOND;
}

}

----------------------------------------------------------------------------------


#int_rtcc // This function is called every time
void clock_isr() { // the RTCC (timer0) overflows (255->0).
// For this program this is apx 76 times
if(--int_count==0) { // per second.
++seconds;
int_count=INTS_PER_SECOND;
}

}


void main() {

BYTE start;

int_count=INTS_PER_SECOND;
set_timer0(0);
setup_counters( RTCC_INTERNAL, RTCC_DIV_256 | RTCC_8_BIT);
enable_interrupts(INT_RTCC);
enable_interrupts(GLOBAL);

do {

printf("Press any key to begin.\n\r");
getc();
start=seconds;
printf("Press any key to stop.\n\r");
getc();
printf("%u seconds.\n\r",seconds-start);

} while (TRUE);

}

-----------------------------------------------------------------------------

[inservi]

Hello Nina,

This program use 'interrupt' mechanism.

A counter (RTCC) is setup to the line :
setup_counters( RTCC_INTERNAL, RTCC_DIV_256 | RTCC_8_BIT);.

This counter is incremented automatically by the PIC's hardware. With the previous setup, if the external clock is 20Mhz, the counter will overflow every 13mS.
Each time the counter is overflow, the PIC call the function declared after '#int_rtcc' (void clock_isr() in your example.).

The interrupts must be enables with the following lines :

enable_interrupts(INT_RTCC);
enable_interrupts(GLOBAL);

There are some other interrupt and generally other counters depending on the PIC used.

dro.
_________________
in médio virtus

[nina]

but when and where the interrupt will be called?

tks

nina

[inservi]

Hello Nina,

When: every time the counter overflow (about every 13mS in this case).
Where: internally. From the hardware circuitry for control timer and interrupt.

dro.
_________________
in médio virtus

[nina]

thank you very much inserv

I will try to implement and If appear others doubt I post here.
Thanks again

Nina