3.15 __nested Keyword

The IAR __nested keyword enables interrupts in the prologue of an interrupt handler, that is it allows nested interrupts to occur.

Suggested Replacement

There is an MPLAB XC8 attribute and specifier that together perform a similar tasks to this keyword.

Use the MPLAB XC8 interrupt attribute in addition to the __interrupt(number) specifier. The ISR_NOBLOCK macro can be used as an alias for __attribute__((interrupt)) if preferred.

Caveats

The Common C Interface must be enabled using -mext=cci to use the __interrupt qualifier.

Examples

Consider migrating IAR code such as:

volatile int x;
#pragma vector=2
void __nested __interrupt incIsr(void) {
    x++;
}

to MPLAB XC8 code similar to:

#include <xc.h>
 
volatile int x;
void __attribute__((interrupt)) __interrupt(2) incIsr(void) {
    x++;
}

Further Information

See the Interrupts section in the MPLAB XC8 C Compiler User's Guide for AVR MCUs for more information on writing interrupt functions.