What language/tool ?
What PIC type ?
What is this "GOTO" and "DEFINE" ? Doesn't look as MPASM !?
What is "asm" and "endasm" ?
Why is only the retfie instruction starting in pos 1 ?
Why restore w, status and pclath if you don't save them ?

Jan-Erik



-----Original Message-----
From: David Dunn [mailto:ddunn@TCAINTERNET.COM]
Sent: den 26 september 2003 22:02
To: PICLIST@MITVMA.MIT.EDU
Subject: [PIC]: Interrupts


I'm at wits end here, for some reason my ISR doesn't seem to be working. I'm monitoring '_TENTHS' in the main
program loop and it's not incrementing.  Have I missed something obvious ?  What kinds of things would keep the
TIMER0 interrupt from running ?

Thanks for any ideas.


DLD

--------------------------------------------------------------------------------------------------------------


wsave           var     BYTE    $020 SYSTEM
wsave1  var     BYTE    $0a0 SYSTEM
wsave2  var     BYTE    $120 SYSTEM
wsave3  var     BYTE    $1a0 SYSTEM
ssave           var     BYTE    BANK0 SYSTEM
psave           var     BYTE    BANK0 SYSTEM

GOTO AFTERINT                              'Jump past interrupt handler

DEFINE INTHAND isr

asm

isr                             ; int handler begins here

    ;bsf     portb,7

    btfsc   INTCON,1            ; test if external interrupt (portb.0) occurred
    goto    portbint            ; jump over to (portb.0) int handler. otherwise, just fall thru to TIMER0 handler

timer0int

    movlw       0x9e                        ;reload timer with (256 - (1)200) + 2 (3a for .1, 9e for .05)
    movwf       TMR0
    incf        _TENTHS                 ;increase TENTHS value
    bcf         INTCON,2                    ;clear tmr0 interrupt flag
    goto    exitisr

portbint

    movf    TMR1H,W            ;read value on timer1
    movwf   _TMR1HI            ;store it in some variable
    movf    TMR1L,W
    movwf   _TMR1LO

    clrf    TMR1L              ;load timer1 with zero again
    clrf    TMR1H

    bcf         INTCON,1                    ;clear rb0 interrupt flag

exitisr
                                ;restorecode follows here
        movf    psave,w
        movwf   PCLATH
        swapf   ssave,w
        movwf   STATUS
        swapf   wsave,f
        swapf   wsave,w

retfie

endasm

AFTERINT:

    ' set up timer0
    TMR0        = 0
    INTCON      = %00000000
    OPTION_REG  = %11000111
    INTCON      = %10100000

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