Mike,

That's interesting, I've just gone back and looked at the interrupts
section in my book and I'd totally missed that bit :( Though in my
defence they had hidden that part away beyond the next section, but
still... I'll fix that and see if it helps. Thanks for pointing it
out...

Matt

On Tuesday 30 March 2004 15:58, Michael Rigby-Jones wrote:
> >-----Original Message-----
>
> From: Matt Marsh [mailto:matt@MATTMARSH.NET]
>
> >So, the program should start and light the LED by default.
> >When I press the button for the first time the LED should go
> >out and stay out until the system is reset. However, the LED
> >just comes on and stays on.
> >
> >Here is the code:
> >ISR
> >        clrwdt
> >        bcf     INTCON,3        ; Reset timer interrupt
> >
> >        movlw   d'1'            ; Subtract 1 from sequence
> > number to subwf   SEQ,w           ; make it zero based
> >        addwf   PCL,f
> >        goto    Sequence1
> >        goto    Sequence2
>
> The first thing I noticed about this is that you are not
> performing any context saving!  You are modifying W both here and
> in the main loop (when a button is pressed).  You should be
> saving any registers that the main loop isn't expecting to get
> clobbered before doing anything else in your ISR. The datasheet
> for the PIC you are using should have some example code that
> shows how to save STATUS and W which are generaly the most
> important two.
>
> Regards
>
> Mike
>
>
>
>
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Matt N. Marsh
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