clark scrobe on the papyrus:

> Greetings all,
> 
> In trying to assist an associate with problems developing code for an
> RF comb filter board designed around a Mega16, things are, well,
> actting really weird, to say the least.  It almost seems to be a
> development tool problem, but I am really baffled.  I am using ICCAVR
> (6.28C), AVR Studio (4.11, build 10, SP3), and a JTAGICE mk II
> emulator.
> 
> This is a fairly small program, consisting of main, a couple of small
> (inline assembly) routines, and a Timer1 OC interrupt (in C). I will
> try to make my description as concise as possible.  We got around the
> original problem (i.e. the filtering itself) by making every variable
> in main (about 100 bytes or so, total) static, thus taking them off of
> the software stack.   This suggested one of a couple of things:  a bad
> sector or two in upper RAM, or a memory setup problem.  Well, I raped
> a very simple memory test routine (write, read, complement, repeat)
> from another project that apparently runs fine on a Mega16, made it a
> single function program, i.e. main( ), compiled it in the ICC IDE,
> then tried to load it an run it.
> 
> It is a stand-alone, non bootloader, type program.  To start, we tried
> it on the same prototype board we had been working on. A reset sends
> to a seemingly random starting point in the code (although actually
> one of several distinct locations), using the recommended C startup
> file crtatmega.o.  An AVR Studio soft reset often performs more like a
> single-step, sometimes sends it to one of those same "random"
> locations, and sometimes sends it off into the weeds.
> 
> In an attempt to make some sense of things, I got my hands on an old
> board with a different end usage, but also built around the Mega16,
> and it performed identically.  I have tried every combination of fuse
> bits that makes any sense whatsoever, we use no lock bits, and I am
> just really at a loss.
> 
> Anyone know of any weirdness between the Mega16 and these tools, or
> have any other ideas?
> 
> Thanks,
> Clark

It sounds like an uninitialised interrupt jump table entry. You
probably have a floating pin on INT0 or INT1 and the jump table entry
is taking the code to unpredictable locations. The behaviour of Studio
is strange, as that is usually quite stable.

I suggest you go here:

 http://www.imagecraft.com/software/ 

and join the ICCAVR mailing list. There are a lot of helpful people
there. You will need to share some code so that the problem can be
traced.

-- 
John B

Greetings all,

In trying to assist an associate with problems developing code for an
RF comb filter board designed around a Mega16, things are, well,
actting really weird, to say the least.  It almost seems to be a
development tool problem, but I am really baffled.  I am using ICCAVR
(6.28C), AVR Studio (4.11, build 10, SP3), and a JTAGICE mk II
emulator.

This is a fairly small program, consisting of main, a couple of small
(inline assembly) routines, and a Timer1 OC interrupt (in C). I will
try to make my description as concise as possible.  We got around the
original problem (i.e. the filtering itself) by making _every_ variable
in main (about 100 bytes or so, total) static, thus taking them off of
the software stack.   This suggested one of a couple of things:  a bad
sector or two in upper RAM, or a memory setup problem.  Well, I raped a
very simple memory test routine (write, read, complement, repeat) from
another project that apparently runs fine on a Mega16, made it a single
function program, i.e. main( ), compiled it in the ICC IDE, then tried
to load it an run it.

It is a stand-alone, non bootloader, type program.  To start, we tried
it on the same prototype board we had been working on. A reset sends to
a seemingly random starting point in the code (although actually one of
several distinct locations), using the recommended C startup file
crtatmega.o.  An AVR Studio soft reset often performs more like a
single-step, sometimes sends it to one of those same "random"
locations, and sometimes sends it off into the weeds.

In an attempt to make some sense of things, I got my hands on an old
board with a different end usage, but also built around the Mega16, and
it performed identically.  I have tried every combination of fuse bits
that makes any sense whatsoever, we use no lock bits, and I am just
really at a loss.

Anyone know of any weirdness between the Mega16 and these tools, or
have any other ideas?

Thanks,
Clark