High Priority Timer on a PIC18F2550, XC8

This example demonstrates a high priority interrupt on the PIC18F2550 and MPLABX 3.40 IDE with the XC 1.38 compiler. Make sure YOU remove the spaces WordPress throws in, if not your compiler will whine.

Sorry, I can’t assist if you have a C18 compiler or PIC16.

#include  //Remove space between c and period

#define USE_AND_MASKS

void SetupHighPriorityTMR1(void);
void ClearTMR1Flag(void);
void DoHPStuff(void);

void main(void)
{
 SetupHighPriorityTMR1();

 while (1);
}

/* This function is called when the interrupt is triggered */
void interrupt HighPriorityInterrupt(void)
{
 if (TMR1IE & & TMR1IF) //Remove space between amperstands
 {
 ClearTMR1Flag();
 DoHPStuff(); //Do what you need here.  I call a function.
 }
}

//Setup is called once.
void SetupHighPriorityTMR1(void)
{
 IPEN = 1; //Enable priority levels < Set this first!
 TMR1IE = 1; //Timer1 Overflow Interrupt Enable bit 
 TMR1IP = 1; //Timer1 Overflow Interrupt Priority bit 
 PEIE = 1; //Enable Peripheral Interrupt Enable register
 GIEH = 1; //Enable HIGH global interrupts < Set this last!

 ClearTMR1Flag();
}

//Clear is called after each interrupt, resets the cycle.
void ClearTMR1Flag(void)
{
 TMR1ON = 0; //Timer1 OFF 
 TMR1H = 0x85; //Timer1 Reset register high byte (1 cycle/.996678 secs)
 TMR1L = 0xC2; //Timer1 Reset register low byte 
 TMR1IF = 0; //Timer1 Clear interrupt flag 
 TMR1ON = 1; //Timer1 ON
}

//Do very little function which maintains a trigger count.
unsigned int hpcycles = 0;
void DoHPStuff(void)
{
 hpcycles++;
}

//Remove this stupid xc tag.

 

// PIC18F2550 Configuration Bit Settings

// 'C' source line config statements

// CONFIG1L
#pragma config PLLDIV = 1 // PLL Prescaler Selection bits (No prescale (4 MHz oscillator input drives PLL directly))
#pragma config CPUDIV = OSC4_PLL6// System Clock Postscaler Selection bits ([Primary Oscillator Src: /4][96 MHz PLL Src: /6])
#pragma config USBDIV = 1 // USB Clock Selection bit (used in Full-Speed USB mode only; UCFG:FSEN = 1) (USB clock source comes directly from the primary oscillator block with no postscale)

// CONFIG1H
#pragma config FOSC = INTOSCIO_EC // Oscillator Selection bits (Internal oscillator, port function on RA6, EC used by USB (INTIO))
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
#pragma config IESO = OFF // Internal/External Oscillator Switchover bit (Oscillator Switchover mode disabled)

// CONFIG2L
#pragma config PWRT = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOR = OFF // Brown-out Reset Enable bits (Brown-out Reset disabled in hardware and software)
#pragma config BORV = 3 // Brown-out Reset Voltage bits (Minimum setting 2.05V)
#pragma config VREGEN = OFF // USB Voltage Regulator Enable bit (USB voltage regulator disabled)

// CONFIG2H
#pragma config WDT = OFF // Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))
#pragma config WDTPS = 32768 // Watchdog Timer Postscale Select bits (1:32768)

// CONFIG3H
#pragma config CCP2MX = ON // CCP2 MUX bit (CCP2 input/output is multiplexed with RC1)
#pragma config PBADEN = ON // PORTB A/D Enable bit (PORTB<4:0> pins are configured as analog input channels on Reset)
#pragma config LPT1OSC = OFF // Low-Power Timer 1 Oscillator Enable bit (Timer1 configured for higher power operation)
#pragma config MCLRE = ON // MCLR Pin Enable bit (MCLR pin enabled; RE3 input pin disabled)

// CONFIG4L
#pragma config STVREN = ON // Stack Full/Underflow Reset Enable bit (Stack full/underflow will cause Reset)
#pragma config LVP = OFF // Single-Supply ICSP Enable bit (Single-Supply ICSP disabled)
#pragma config XINST = OFF // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode disabled (Legacy mode))

// CONFIG5L
#pragma config CP0 = OFF // Code Protection bit (Block 0 (000800-001FFFh) is not code-protected)
#pragma config CP1 = OFF // Code Protection bit (Block 1 (002000-003FFFh) is not code-protected)
#pragma config CP2 = OFF // Code Protection bit (Block 2 (004000-005FFFh) is not code-protected)
#pragma config CP3 = OFF // Code Protection bit (Block 3 (006000-007FFFh) is not code-protected)

// CONFIG5H
#pragma config CPB = OFF // Boot Block Code Protection bit (Boot block (000000-0007FFh) is not code-protected)
#pragma config CPD = OFF // Data EEPROM Code Protection bit (Data EEPROM is not code-protected)

// CONFIG6L
#pragma config WRT0 = OFF // Write Protection bit (Block 0 (000800-001FFFh) is not write-protected)
#pragma config WRT1 = OFF // Write Protection bit (Block 1 (002000-003FFFh) is not write-protected)
#pragma config WRT2 = OFF // Write Protection bit (Block 2 (004000-005FFFh) is not write-protected)
#pragma config WRT3 = OFF // Write Protection bit (Block 3 (006000-007FFFh) is not write-protected)

// CONFIG6H
#pragma config WRTC = OFF // Configuration Register Write Protection bit (Configuration registers (300000-3000FFh) are not write-protected)
#pragma config WRTB = OFF // Boot Block Write Protection bit (Boot block (000000-0007FFh) is not write-protected)
#pragma config WRTD = OFF // Data EEPROM Write Protection bit (Data EEPROM is not write-protected)

// CONFIG7L
#pragma config EBTR0 = OFF // Table Read Protection bit (Block 0 (000800-001FFFh) is not protected from table reads executed in other blocks)
#pragma config EBTR1 = OFF // Table Read Protection bit (Block 1 (002000-003FFFh) is not protected from table reads executed in other blocks)
#pragma config EBTR2 = OFF // Table Read Protection bit (Block 2 (004000-005FFFh) is not protected from table reads executed in other blocks)
#pragma config EBTR3 = OFF // Table Read Protection bit (Block 3 (006000-007FFFh) is not protected from table reads executed in other blocks)

// CONFIG7H
#pragma config EBTRB = OFF // Boot Block Table Read Protection bit (Boot block (000000-0007FFh) is not protected from table reads executed in other blocks)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#include //Remove space between c and period.  //Remove this stupid xc tag.
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