PIC16F73 - RB Port Change Interrupt

**Sadlercomfort** · 09-11-2015

I'm trying to practice using interrupts so I can make use of them when developing PIC programs. Here I'm using the 'RB Port Change Interrupt' with the 'RB Port Change Flag Bit'.

There is no need to set the IOCB register here, because my pic16f73 doesn't support it.

Here's the problem:
When I execute the program and simulate an RB input, the flag bit goes high a successfully enters the Interrupt section. However, at the end of the Interrupt function the 'RBIF=0' command doesnt work, and I cannot enter the interrupt again when simulating an RB input.

Please help.

**stahta01** · 09-11-2015

Code:

void interrupt ISR(void)
{

RBIE=0;					//Disable RB Port Change Interrupt
PORTC=0b10101010;
GIE=1;					//Enable Global Interrupt
RBIF=0;					//Disable RB Port Change Flag Bit
}

I am guessing your C compiler saves the PIC regs that are normally needed to be saved and the restores them on leaving the routine.

But, I would guess that you need to add a statement at the end to re-enable the
interrupt. Like below. I also re-order the statements in what I think is a better way.

Code:

void interrupt ISR(void)
{
RBIE=0;					//Disable RB Port Change Interrupt
PORTC=0b10101010;
RBIF=0;					//Disable RB Port Change Flag Bit
RBIE=1;					//Enable RB Port Change Interrupt
GIE=1;					//Enable Global Interrupt
}

I have no idea why you have the "RBIF=0;" command; but, normally re-enable Interrupt are at the end right before restoring saved regs (that your compiler likely does).

Tim S.

**Sadlercomfort** · 09-11-2015

Hi Tim S.

Your code looks fine, I know thats how it should be, but now the interrupt keeps looping. The RBIF Flag Bit wont change back to 0, when i simulate it executes the 'RBIF=0;' command but the register stays at 1.

I forgot to remove the "RBIF=0;" command, i understand why its not needed,

**Sadlercomfort** · 09-11-2015

I think its a bug in the program, when user RB4 as my flag bit and it goes into the interrupt function i set "RB4=0". Now it seems to exit the interrupt function correctly, I can also set my flag bit again to go back into the interrupt without any problems.

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