Problem with delay_ms

[Guest]

hi there

i know that i'm a greenhorn, which could cause a very simple solution for my problem. but i can't find any solution


problem:
a led should be on for exactly 1000ms (delay_ms(1000)).
but the pin is high for about 1136ms when i use the rtcc (timer0 function with interrupts are necessary for the projekt).

hardware: 16F876@16MHz

code:
#include <PIC_OKW.H>
#include <LCD_DISPLAY.C>
#include <KEYBOARD.C>

#define ints_per_zehntelsekunde 782 // (16000000/(4*256*2))=7812,5 /Sekunde

long int int_zaehler=0; // Interrupt-Zähler auf NULL setzen
long int zehntelsekunden;

#int_RTCC // Funktionsaufruf bei Timer0-Overflow
RTCC_isr()
{ if(--int_zaehler==0)
{++zehntelsekunden;
int_zaehler=ints_per_zehntelsekunde;
}
}


main()
{long int start, zehntel;
/*****************************> SERIELLES GRAFIK-DISPLAY <*****************************/
LCD_INIT_ON();printf("Timer0_OKW2.c%c",0);delay_ms(2000);CLEAR();

/*****************************> TASTATUR konfigurieren <*****************************/
KEYBOARD_INIT();CLEAR_UP();

/*****************************> T I M E R 0 aktivieren <*****************************/
int_zaehler=ints_per_zehntelsekunde;
set_timer0(0);
setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
enable_interrupts(INT_RTCC);
enable_interrupts(global);

do
{

delay_ms(4000);
output_high(pin_C5);
delay_ms(1000);
output_low(pin_C5);

}while(true);

}

p.s.excusing my bad english

[Mark]

The delay_ms function doesn't account for time spent in an interrupt. So during that 1000ms your interrupt took up 136ms. You could setup a timer to count some unit of measurement (I like to use ms). Then do something like