Hi Alvaro,

Thanks for your feedback. I did suspect an index might be going crazy as you
suggest, but I haven't tracked anything down so far. I'll give it another
careful look.

James

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Alvaro Deibe Diaz
> Sent: 27 April 2005 09:18
> To: 'Microcontroller discussion list - Public.'
> Subject: RE: [PIC] HiTech C and Local Variables
>
>
> Hi, James.
>
> I had troubles with RAM in F877's some time ago. PICC 8.05PL2,
> and MPLAB5.x.
>
> It was a difficult problem to track, as yours, but in my case i was
> experimenting resets now and then... impossible to track with the
> emulator.
> Only happening in the "real" environment.
>
> Finally i came across a problem with a vector index getting crazy
> (my guilt,
> of course). PICC uses the FSR to access vectors, so a wrong index
> can access
> anywhere in the RAM. In my case, it was accessing the program counter, and
> that was the cause for the resets.
>
> PICC puts local and static variables in different places, thus
> changing your
> local variable to static can get it away from the problem. But the problem
> is still there.
>
> I've updated past month to 8.03PL3 (untill the end of some projects), so I
> have little experience with this release. But no problem so far.
>
> Regards,
>
> Alvaro Deibe Diaz.
>
> > -----Mensaje original-----
> > De: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]
> > En nombre de James
> > Enviado el: martes, 26 de abril de 2005 14:44
> > Para: Microcontroller discussion list - Public.
> > Asunto: [PIC] HiTech C and Local Variables
> >
> > I'm wondering if anyone else has come across strange
> > behaviour sometimes when using local function variables with
> > HiTech's PIC C compiler (latest version - 8.05PL2, and also 8.03PL3)?
> >
> > The contents of temporary local variables in some of my
> > functions are getting overwritten without reason. By changing
> > them to static it fixes the problem.
> >
> > I'm having to allocate a lot of the other variables in 3 of
> > the banks, so I'm wondering if that is a cause? I've turned
> > off all optimization and it still happens. At no point does
> > any of my code write to an address in RAM except via a
> > pointer to a variable, so I can't see how these variables are
> > getting overwritten.
> >
> > What makes it so much harder to track down is that it doesn't
> > happen in the MPLAB similuator but only when I program the
> > PIC, of course! ;) So I'm debugging with a scope and some
> > diagnostic pin output...
> >
> > I've been using this compiler for a couple of years without
> > this trouble before, but with this code it's happening all
> > over the place. I've never targeted this PIC (16F876A)
> > before, but I doubbt that's central to it.
> >
> > I could raise this on HiTech's forum but that gets little
> > traffic. I'm really looking for any experiences from people
> > here that could backup or otherwise what I think I'm seeing!
> > Many thanks.
> >
> > James
> >
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