On 2011-06-01, at 10:34 AM, RussellMc wrote:

> I was thinking of setting up the stack in a manner such that the
> footprints of the original setup were still visible.
> When you start you have the system under explicit control and can
> produce stack writes of known content.
> Subsequently it may be possible to perform some action which depends
> on the stack having the original value.
> Tasks which "run out the door" when popped may be able to be trapped
> almost immediately by a timer  interrupt.
>=20
> If "the stack wraps silently, as noted, it may be possible to work it
> down to "empty" and then pop again to "wrap silently" so you are at
> the top of the stack and working down. Calls with original data in
> would pop to locations which were known. When you got a pop that did
> something different you'd know the original value had been
> overwritten. You may have one chance in 2^stack_address_bits of
> missing a corruption if popping single addresses.

Unfortunately, for the PIC16f886, the only access to the stack happens with=
 the call, interrupt and return instructions. There is no other access. I t=
hink the only option is to instrument round the instructions in ones own co=
de.

Since the OP was looking for a way to determine stack depth in use, overflo=
w and underflow, this would satisfy the requirement in these restrictive ci=
rcumstances. One could monitor these in a mirrored stack to look at where t=
he faults are happening, which I where I think you are going with this Russ=
ell.



--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.