Electronic – I having troubling understand what other interrupt firing besides TMR2 on PIC18f4550

interruptspictimer

I having troubling understand what other interrupt firing high_isr besides TMR2 on PIC18f4550.

Way I detect it I set pin MY_DBG_PIN toggling everytime high_isr is activated, and from what I try to do, only TMR2 I have activated and nothing else.

My code looking like:

#include <p18f4550.h>

#define USE_OR_MASKS

#include <pwm.h>
#include <timers.h>

#pragma config PLLDIV = 10
#pragma config FOSC = ECPLLIO_EC

#pragma config PWRT = OFF
#pragma config BOR = OFF
#pragma config MCLRE = ON
#pragma config PBADEN = OFF
#pragma config ICPRT = OFF
#pragma config LVP = OFF
#pragma config WDT = OFF,DEBUG=OFF

/* Sets the PWM value on CCP1 to 50% duty cycle*/

#define MY_DBG_PIN        LATBbits.LATB1 
#define MY_DBG_PIN_TRIS   TRISBbits.TRISB1

#pragma interrupt high_isr
void high_isr (void)
{
    //* Comment to notice toggling of MY_DBG_PIN at 0.7Mhz
    if(PIR1bits.TMR2IF)         // Timer 2 interrupt
    {
        MY_DBG_PIN = 0;

        PIR1bits.TMR2IF = 0;
    }
    //*/

    // Are some other interrupts also firing? Why?
    //MY_DBG_PIN = 0; // If uncomment, toggling at 0.7Mhz
}

#pragma code high_vector=0x08
void interrupt_at_high_vector(void)
{
    MY_DBG_PIN = 1;
    _asm GOTO high_isr _endasm
}
#pragma code /* return to the default code section */

void main (void)
{
    TRISC=0;
    OpenTimer2(TIMER_INT_ON | T2_PS_1_4 | T2_POST_1_16 );
    OpenPWM1( 149 );
    SetDCPWM1( 300 );

    MY_DBG_PIN_TRIS = 0;    // make it an output 

    PIE1bits.TMR2IE=1;           //enable Timer2 interrupt
    INTCONbits.PEIE=1;          //enable peripheral interrupts
    INTCONbits.GIE=1;           //enable glogal interrupts
    INTCONbits.GIEH = 1; /* Enable global Interupt */

    while(1)
    {
    }
}

As can see, only TMR2 possibly fire ISR, but then do you notice high freq. update of debugging pin if you uncomment the line?

If I specify TMR2 interrupt flag in ISR and then toggle debugging pin, then expected update freq, as current active code is like.

What other thing can be triggering ISR and how I check that without checking flags of all interrupts?

Best Answer

If I understand right, then when you comment the first (larger) bit out and uncomment the second bit it toggles at 0.7MHz?
The interrupt flag is not cleared so it will immediately jump back to the ISR. The second bit is not in an if statement so it will always be executed. So it will keep setting the pin in the interrupt_at_high_vector and clearing it in high_isr. You need to make sure the flag is always cleared (if it is not cleared automatically)
What are you wanting it to do?

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