Interrupt usage

[Russ Kincaid]

I am a neophyte and don't understand why my code is not working. The statement: on interrupt goto wait is said to be bad syntax but I don't believe it, something else is wrong. My program:
REM device = 12F675
CMCON = 7 ' SETS DIGITAL MODE
ANSEL = 0 ' GPIO.0 TO GPIO.3 SET AS DIGITAL
OPTION_REG = 0 ' WEAK PULLUPS ENABLED
TRISIO = %00000100 ' GPIO.2 SET AS INPUT
IOC = %00000100 ' INTERRUPT ENABLED ON GPIO.2
INTCON = %10010000 ' INTERRUPT ENABLED
N VAR BYTE ' VARIABLE N DEFINED
' ************************************************** ***********
START:
ON INTERRUPT GOTO WAIT
HIGH GPIO.0
FOR N=1 TO 13
NAP 6
NEXT N
LOW GPIO.0

WAIT:
DISABLE INTERRUPT
SLEEP
ON INTERRUPT GOTO START
ENABLE INTERRUPT 'do i need to clear the interrupt bit first?
END

[mister_e]

i see quite a few mistake here

1. there's no Goto Start after your LED blink
2. Disable INTERRUPT is not placed at the right place
3. you can't have more than 1 ON INTERRUPT GOTO
4. the first ON INTERRUPT is not a the right place
5. not sure about the NAP loop... to me PAUSEUS would be a better option
6. not sure about SLEEP in the ISR
7. yes you MUST clear INT flag
8. There's no RESUME at the end of your ISR
9. WAIT is a reserved word and can't be used for labels

but the rest is OK

Something like bellow should work

    @ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

    CMCON = 7               ' SETS DIGITAL MODE
    ANSEL = 0               ' GPIO.0 TO GPIO.3 SET AS DIGITAL

    OPTION_REG = 0          ' WEAK PULLUPS ENABLED
                            ' GP2/INT on falling edge
                            
    TRISIO = %00000100      ' GPIO.2 SET AS INPUT

    GPIO = 0

    N VAR BYTE              ' VARIABLE N DEFINED
    
    ON INTERRUPT GOTO WAIT_int    
    INTCON = %10010000      ' INTERRUPT ENABLED

  '  *************************************************************
START:
            TOGGLE GPIO.0
            FOR N=0 TO 250
                pauseus 1000
                NEXT
            GOTO START
                     
DISABLE        
WAIT_INT:
            TOGGLE GPIO.1
            INTCON.1=0      ' Clear GP2/INT flag
            RESUME
            ENABLE
            
            END

[Russ Kincaid]

Thanks for the info. Since I can't have more than one interrupt goto, I will have to re-think my program. I would like to have the program wake from sleep on interrupt. Could I use "on interruupt goto start"? I want it to end up in sleep mode, do I need a resume statement?
My program is:
Turn LED on
Wait 15 minutes
Turn LED off
Go to sleep
Optionally, I would like to turn the LED off in less than 15 minutes, using the interrupt; but that does not seem possible. I guess I will have to have two buttons: a start (interrupt) button and stop (goto sleep) button.
This program compiles OK, what do you think?


REM device = 12F675
CMCON = 7 ' SETS DIGITAL MODE
ANSEL = 0 ' GPIO.0 TO GPIO.3 SET AS DIGITAL
OPTION_REG = 0 ' WEAK PULLUPS ENABLED
TRISIO = %00001100 ' GPIO.2 AND GPIO.3 SET AS INPUT
IOC = %00000100 ' INTERRUPT ENABLED ON GPIO.2
N VAR WORD ' VARIABLE N DEFINED
ON INTERRUPT GOTO START
INTCON = %10010000 ' INTERRUPT ENABLED
' ************************************************** ***********
START:

HIGH GPIO.0
FOR N=1 TO 900
IF GPIO.3=0 THEN SLEEPNOW
PAUSE 1000
NEXT N
SLEEPNOW:
LOW GPIO.0
SLEEP 65535 ' DOES IT EVENTUALLY WAKE UP? (I DON'T WANT IT TO)

END

[mister_e]

What else the pic will need to do? There's some case you don't even need any ON INTERRUPT.

@ SLEEP will send the PIC in sleep mode untill there's a interrupt type who can wake up the PIC. It should be listed in your datasheet, somewhere at the end.

[Brian J Walsh]

My understanding is, that although there are many sources of interrupts possible within the PIC's hardware, there is only one resulting interrupt condition. Either the processor has been interrupted or it has not. This leads me to believe that this interrupt condition has to be dealt with by a single interrupt handling routine which tells the interrupted processor what to do.

The interrupt routine, or interrupt handler, in its execution could, of course, determine the source of the interrupt by investigating the various interrupt flags and take specific action appropriate to the source, but there is only one routine and the point in the program (the label) where it is located is stated in the 'ON INTERRUPT GOTO' statement. Having more than one 'ON INTERRUPT GOTO', each with a different label, doesn't make sense to me, as that would mean that the interrupted processor could go to more than one routine to resolve the interrupt. How would it know which to go to ?

The flexibility allowed by MELabs by not predetermining the label in the command just means that you can call your interrupt handler what you like. It doesn't mean that there can be more than one and that they are differentiated by having different labels.

OK.. now to the question! The 'ON INTERRUPT' statement reference on MELabs PIC BASIC Pro support website, clearly states before giving the syntax example, that "More than one ON INTERRUPT may be used in a program"... Is this a typo or have I got it completely wrong?

Brian Walsh

[Darrel Taylor]

Hi Brian,

It's NOT a typo. You can use all available interrupts simultaneously.

On any interrupt, the program flow will be directed to the single interrupt handler. Then it's up to you to determine which one fired.

Each interrupt source has 2 bit's associated with it. An Enable bit (*IE), and an Interrupt Flag (*IF). You need to look in the datasheet to find where those bit's are.

Then in the interrupt handler, check BOTH the enable bit and the interrupt flag to determine if a particular interrupt has triggered.

For example, to have the RB Port change and Timer1 interrupts, it might look something like this...

RBIE    VAR INTCON.3
RBIF    VAR INTCON.0
TMR1IE  VAR PIE1.0
TMR1IF  VAR PIR1.0
TMR1ON  VAR T1CON.0

OldBits VAR BYTE
NewBits VAR BYTE


OldBits = PORTB   ; End the mismatch
RBIF = 0          ; clear the flag
RBIE = 1          ; enable PORTB change interrupts

TMR1IF = 0        ; clear TMR1 interrupt flag
TMR1IE = 1        ; enable Timer1 interrupts
TMR1ON = 1        ; Start the Timer

ON INTERRUPT GOTO INTHandler

Main:
    PAUSEUS 20
GOTO Main

DISABLE
INTHandler:
    IF RBIE and RBIF THEN
        NewBits = PORTB  ; end the mismatch
        RBIF = 0         ; clear the flag
        ; handle RB port change interrupt here
        OldBits = NewBits
    ENDIF

    IF TMR1IE and TMR1IF THEN
        TMR1IF = 0       ; clear the flag
        ; handle Timer1 interrupt here
    ENDIF
RESUME
ENABLE

hth,