timer.c

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/*
 * main timing control
 *
 * (c) 2007 by Matthias Arndt <matthias.arndt@tu-clausthal.de>
 *
 * we generate Timer interrupts every single ms and signal if 62ms have passed
 * this generates a semaphore signal which in turn activates sensor sampling in the main loop
 */

#include "t89c51cc02.h"
#include "datatypes.h"
#include "timer.h"

volatile bit measurement_task; 

BYTE timekeeper;

void Timer_init()
{
        measurement_task=0;     

        TR0=0;          /* stop Timer 0 */
        TMOD |= 1;      /* Timer 0 Mode 1 */
        TF0=0;          /* clear timer flag */

        timekeeper=TIMER_MILLISECONDS;

        /* initial timing value */
        TH0=TIMER_RELOAD_H;
        TL0=TIMER_RELOAD_L;
        
        TR0=1;          /* start Timer 0 */
        ET0=1;          /* activate Timer 0 interrupt */
}

void Timer_interrupt(void) interrupt 1 using 2
{
        timekeeper--;
        if(timekeeper==0)
        {
                measurement_task=1;     /* signal next sensor sampling is due */
                timekeeper=TIMER_MILLISECONDS;
        }
        
        /* reload Timer 0 */
        TH0=TIMER_RELOAD_H;
        TL0=TIMER_RELOAD_L;
        TF0=0;          /* acknowledge Timer 0*/
}

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