Bradley wrote:

> I've been developing a small project using a 12C671 and in my
> attempts to break the program, have been able to induce brownout
> program crashes/hangs.

> I'd like to try a software solution to be able to save the
> $0.75 per board. AN607 discusses power up considerations and shows
> two examples of ways that the WDT can be used to detect brownout.


Bradley - Another post recommends the simple resistor-transistor
brownout circuit in the Microchip app notes.  I've used it as well,
with great success.

There is NO  I repeat NO software technique that can guarantee
against brownouts.  Your program can hang anywhere, and do any number
of dangerous things and never reset or WDT timeout.  You can begin
executing code in uninitialised program space, get into a software
loop that never exits because registers never increments, and on and
on and on.  Unless you are designing toys, don't bother trying this
approach.  A hardware brownout circuit will cost you US$0.07, and
will save your ass.

I have seen all of the above problems.

I'd be glad to post a diagram for my brownout tester machine (PIC
based, of course) if you are interested.


Best Regards,

Lawrence Lile