Hi Circuiteers. I can't find an answer to this. All I want to do is wake my PIC24F04KL device when a button is pressed. I thought I'd get away with the below
in init()

    // IoC
    IFS1bits.CNIF       = 0;  // clear CN IF
    IEC1bits.CNIE       = 1; // change notification
    CNEN2bits.CN29IE    = 1; // pin 5, button

in main()

    while(1)
    {
        Sleep();
       IFS1bits.CNIF       = 0;  // clear CN IF
        LED = 1;
        __delay_ms(10);
        LED = 0;
    }

However this results in a device reset on a button press. To make it work I have to define the interrupt vector below

void __attribute__((__interrupt__, auto_psv )) _ISR _CNInterrupt (void)
{
    IFS1bits.CNIF       = 0;  // clear CN IF
}

I thought in the past I've got away without doing this, but perhaps that was on a PIC16 or PIC18, or perhaps I'm misremembering entirely

 

If you do not define the ISR then your system will do weird things or crash.
Try not enabling the CNIE bit.

 

Worth a try but that didn't work. The device stayed asleep indefinitely with the CN disabled

 

Worth a try but that didn't work. The device stayed asleep indefinitely with the CN disabled

Right, of course. The MCU needs an interrupt to wake up.

 

It's no biggie. I'll just have to implement the barebones interrupt vector.

 

The reason you may have gotten away with it in the past depends on the default MCU memory settings when no ISR is in place.