When do you save pclath, etc? You have to save them on entry to the isr or
they will change in your mainloop.




----- Original Message -----
From: "David Dunn" <ddunn@TCAINTERNET.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, September 26, 2003 1:01 PM
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
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.