PIC32MZ tutorial -- Timer Interrupt

　　An interrupt is an internal or external event that requires quick attention from the controller. The PIC32MZ architecture provides a rich interrupt system that can manage up to 190 sources of interrupts. Each interrupt source can have a unique piece of code, called the Interrupt Service Routine (ISR) directly associated via a pointer, also called a "vector", to provide the required response action.

　　At the moment, I use Timer1 interrupt as a example to show how to enable interrupt and how to write interrupt service routine for PIC32MZ. The implementation has three parts. The first is the Timer1 interfaces. The second is interrupts interfaces. And the third is the Timer1 interrupt service routine.

　　The Timer1 interfaces include TMR1_Open() and TMR1_Write(). In the TMR1_Open(), will enable Timer1 and Timer1 interrupt. configure Timer1 to overflow and interrupt per millisecond. set Timer1 interrupt priority level and subpriority level. Below code show me how to do that.

/**
  <p><b>Function: TMR1_Open</b></p>

  <p><b>Summary: Initialization of Timer </b></p>

  <p><b>Description: TMR1 on; 0.08 microsecond every tick, overflow and interrupt per ms </b></p>

  <p><b>Remarks: Pre-scale 1:8; PB 100MHz; PR1 0x30D3</b></p>
 */
// TODO Insert function definitions (right here) to leverage live documentation
void TMR1_Open(void)
{
    T1CON = 0x8010;
    PR1 = 0x30D3;
    IPC1SET = 0x5;
    IEC0SET = 0x10;
    IFS0CLR = 0x10;
}
// Comment a function definition and leverage automatic documentation 
/**
  <p><b>Function: TMR1_Write</b></p>

  <p><b>Summary: Write TMR1</b></p>

  <p><b>Description: Write a value to TMR1</b></p>

  <p><b>Remarks: the value is range of 0~65535</b></p>
 */
// TODO Insert function definitions (right here) to leverage live documentation
void TMR1_Write(unsigned int value)
{
    TMR1 = value & 0xFFFF;
}

　　The interrupts interfaces include EnableINT(), DisableINT() and SelectMultiVector(). When we want to use any interrupt source, call EnableINT() to enable interrupt module first. PIC32 have two interrupt vector modes, the singlevector mode and multivector mode. SelectMultiVector() will help to set interrputs for multivector mode. I do that like below.

/** 
  @Function
    EnableINT

  @Summary
    Enable interrupts

  @Remarks
    This function need to be called first before using any interrupt source
 */
void EnableINT(void) 
{
    asm volatile("ei");
}

/** 
  @Function
    DisableINT

  @Summary
    Disable interrupts

  @Remarks
    
 */
void DisableINT(void) 
{
    asm volatile("di");
}

/** 
  @Function
    SelectMultiVector

  @Summary
    Set system to use multivector mode for interrupts

  @Remarks
    
 */
void SelectMultiVector(void) 
{
    unsigned long MVEC_MASK = 0x1000;
    INTCONSET = MVEC_MASK;
}

　　At the end, I show the main function and the Timer1 interrupt service routine. There are styles of interrupt service routine, the interrupt attribute style, like 

      __attribute__((interrupt([IPLn[SRS|SOFT|AUTO]]))),  

and the interrupt pragma style, like

       # pragma interrupt function-name IPLn[AUTO|SOFT|SRS] [vector
       [@]vector-number [, vector-number-list]]
       # pragma interrupt function-name single [vector [@] 0

　　It strongly recommend the first style. So there they are.

#include <xc.h>
#include "TMR.h"
#include "Interrupt.h"
#include "ConfigurationBits.h"

//#define LED_IOCTL()    TRISHbits.TRISH0 = 0
//#define LED_SETON()    LATHbits.LATH0 = 1
//#define LED_SETOFF()   LATHbits.LATH0 = 0
//#define LED_OPEN()     ANSELHbits.ANSH0 = 0

//#define LED_IOCTL()    TRISH &= 0xFFFFFFFE
//#define LED_SETON()    LATH |=  0x00000001
//#define LED_SETOFF()   LATH &= 0xFFFFFFFE
//#define LED_OPEN()     ANSELH &= 0xFFFFFFFE

#define LED_IOCTL()       TRISHCLR = (1<<0)
#define LED_SETON()       LATHSET = (1<<0)
#define LED_SETOFF()      LATHCLR = (1<<0)
#define LED_ONOFF()       LATHINV = (1<<0)
#define LED_OPEN()        ANSELH &= 0xFFFFFFFE

volatile unsigned int COUNTER;

void __attribute__((vector(_TIMER_1_VECTOR), interrupt(ipl1AUTO), nomips16)) TMR1_ISR(void)
{
    if (COUNTER++ >= 300)
    {
        COUNTER = 0;
        LED_ONOFF();
    }
    TMR1_Write(0);
    IFS0CLR = 0x10; // Clear flag
 }

void main(void) 
{
    LED_OPEN();
    LED_IOCTL();
    TMR1_Open();
    TMR1_Write(0);
    SelectMultiVector();
    EnableINT();
    COUNTER = 0;
    while (1)
    {
        ; // do nothing
    }
}

　　This application run well on PIC32MZ EC starter kit. I see the LED blink perfectly as expectation.