In this tutorial we will learn how to make PORTB change Interrupt with PIC Microcontroller. Here I am use PIC16F877A Microcontroller and mikroC PRO for PIC compiler.

You can watch the following video or read the written tutorial below.

 

 

Interrupt
Interrupt is a signal Microcontroller emitted by hardware or software indicating and event that needs immediate attention .
 

 PORTB Change Interrupt Control Registers 

 

OPTION_REG Register

The OPTION_REG Register is a readable and writable register, which contains various control bits to configure the TMR0 Prescaler / WDT postscaler.

 

 OPTION_REG REGISTER

 

bit 7             RBPU: PORTB Pull-up Enable bit 

                    1 = PORTB pull-ups are disabled 

                    0 = PORTB pull-ups are enabled by individual port latch values 

 

bit 6             INTEDG: Interrupt Edge Select bit 

                   1 = Interrupt on rising edge of RB0/INT pin 

                   0 = Interrupt on falling edge of RB0/INT pin 

 

bit 5            T0CS: TMR0 Clock Source Select bit 

                   1 = Transition on RA4/T0CKI pin 

                   0 = Internal instruction cycle clock (CLKOUT)  

 

bit 4            T0SE: TMR0 Source Edge Select bit 

                   1 = Increment on high-to-low transition on RA4/T0CKI pin 

                   0 = Increment on low-to-high transition on RA4/T0CKI pin 

 

bit 3            PSA: Prescaler Assignment bit 

                   1 = Prescaler is assigned to the WDT  

                   0 = Prescaler is assigned to the Timer0 module 

 

bit 2-0        PS2:PS0: Prescaler Rate Select bits

 

INTCON Register

The OPTION_REG Register is a readable and writable register, which contains various enable and flag bits for TMR0 register Overflow, RB Port change and External RB0/INT pin Interrupts.


     INTCON REGISTER

 bit 7           GIE: Global Interrupt Enable bit 
                  1 = Enables all unmasked interrupts
                  0 = Disables all interrupts

bit 6           PEIE: Peripheral Interrupt Enable bit   
                  1 = Enables all unmasked peripheral interrupts
                  0 = Disables all peripheral interrupts

bit 5          T0IE: TMR0 Overflow Interrupt Enable bit
                 1 = Enables the TMR0 interrupt
                 0 = Disables the TMR0 interrupt

bit 4          INTE: RB0/INT External Interrupt Enable bit
                 1 = Enables the RB0/INT external interrupt
                 0 = Disables the RB0/INT external interrupt

bit 3           RBIE: RB Port Change Interrupt Enable bit
                  1 = Enables the RB port change interrupt
                  0 = Disables the RB port change interrupt

bit 2           T0IF: TMR0 Overflow Interrupt Flag bit
                  1 = TMR0 register has overflowed (must be cleared in software)
                  0 = TMR0 register did not overflow

bit 1           INTF: RB0/INT External Interrupt Flag bit
                  1 = The RB0/INT external interrupt occurred (must be cleared in software)
                  0 = The RB0/INT external interrupt did not occur

bit 0           RBIF: RB Port Change Interrupt Flag bit
                  1 = At least one of the RB7:RB4 pins changed state; a mismatch condition will continue  to  set the bit. Reading PORTB will end the mismatch condition and allow the bit to be  cleared (must be cleared in software).
                  0 = None of the RB7:RB4 pins have changed state

 

Circuit Schematic of external interrupt

 

Source code:

int i;
void main() {
     TRISB = 0X10;               // RB7 is input pin and other pin is output
     PORTB = 0X00;             // Clear the PORTB register
     INTCON.GIE = 1;       // Enable Global interrupt Enable bit
     INTCON.RBIE = 1;        // RB change interrupt Enable bit
     INTCON.RBIF = 0;        // Clear PORTB on change Flag bit
     OPTION_REG.INTEDG = 1;
     while(1){
              PORTB.F0 = 1;
              delay_ms(250);
              PORTB.F0 = 0;
              delay_ms(250);
              }

}
void interrupt(){
     if(INTCON.RBIF == 1){

                    for(i=0;i<6;i++){                // 6 time blinks
                                     PORTB.F1 = 1;
                                     delay_ms(250);
                                     PORTB.F1 = 0 ;
                                     delay_ms(250);
                                     }
                     INTCON.RBIF = 0;         // clear PORTB on change Flag bit
                    }

     }

 

 

Download free source code

 

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