Michael S. Hagberg wrote:
>
> >Hello again fellow PIClisters,
> >
> >Can someone tell me if it's possible to read a PIC that has had it's
> >protection fuse blown?
>
> YES
>
> >I've heard there's a way to apply a voltage and put it into test mode.
>
> Not exactly, but I will not tell how it's done.
>
> > If I create a programmed chip and protect it, can someone else come along
> and copy it?
>
> YES (see number 1)
>
> Are there any ways to prevent this from happening?
>
> The best (not full proof) way is to zap the program pin with enough voltage
> and current to destroy it without blowing up the chip.
>
> sorry the news isn't better, but not being able to protect the code is no
> reason for not developing a good product and putting it on the market. i am
> much more concerned about someone copying my idea than stealing my code.
>
> michael

  On one circuit I have been working on, the capability to do the job
(controlling HV DC to accomplish this job) in a array of PICs instead of
with a relatively expensive & perishable array of PCs, IS the idea (i.e.
it's easy to do with an expensive array of Pentii, almost impossible to
do with a flock of cheap PICs, but quite cost-effective once you figure
the tricks out.)  In that (admittedly rareish) sort of situation, having
the code stolen means the idea's stolen.  Tough to protect a PIC, in any
better way than you mention, without resorting to pyrotechnic devices &
etc.  (i.e. if you open the case an M-80 blows the chip apart) - Thought
of a good way for this industrial device, though;  Have a fairly
powerful spring which is released to smash the chip if someone breaks
into the control box.  (Rigged like an old caplock musket or like a
modern rifle striker.)  Easy to do that...  Putting 220VDC across
Vdd/Vss would do it, too.  Expect to replace the parts on your next
service call. <G>

  Mark Willis, mwillis@nwlink.com