// case 1: Interrupt Controller available,
// "unconditional interrupt enabling" critical section policy
// (nesting of critical sections _not_ allowed)
//
interrupt void ISR_timer() {  // entered with interrupts locked in hardware
    QF_INT_ENABLE();          // enable interrupts

    QF::TICK_X(0U, &l_ISR_timer); //<-- call the QF tick processing

    QF_INT_DISABLE();         // disable interrupts again
    // send the EOI instruction to the Interrupt Controller
}

// case 2: Interrupt Controller not used,
// "saving and restoring interrupt status" critical section policy
// (nesting of critical sections allowed)
//
interrupt void ISR_timer() {
    QF::TICK_X(0U, &l_ISR_timer); //<-- call the QF tick processing
}