Provide code that implements an interrupt service routine every 20 milliseconds

Question

Provide code that implements an interrupt service routine every 20 milliseconds using timer 1. You may assume that the microcontroller is using a 40MHz SYS_FREQ and that PB_DIV=2. Provide comments to explain what each line does. Your ISR need only clear the interrupt flag and set a variable called tick_flag that has already been declared and initialised to zero. Provide code that initialises the timer and interrupt systems. The ISR has a function prototype of type:

                                    void __ISR(_TIMER_1_VECTOR, ipl2) yourhandler(void);

              should be used to contain the code for your interrupt service routine.

Provide code for an interrupt service routine and an initialisation routine that allows use of timer2 and timer 3 to provide a 5 second interrupt.

Explanation / Answer

void __ISR(_TIMER_1_VECTOR, ipl2) _Timer1Handler(void)
{
LATDINV = 0x0001;
mT1ClearIntFlag(); // clear the interrupt flag
}

void __ISR(_TIMER_2_IRQ, IPL3) Timer2Handler(void) // Function d'interruption Timer 2
{
LATD= 0x0002;
IFS0CLR = 0x00000100; // Clear timer interrupt status flag
T3CONSET = 0x8000;
}
void __ISR(_TIMER_3_VECTOR, IPL3) Timer3Handler(void) // Function interrupt Timer 3
{
LATD= 0x0001;
IFS0CLR = 0x00001000; // Be sure to clear the Timer 2 interrupt status
}

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