>If you pick some part other than an 'F84 solely on the basis of what you've
>heard about the 'C84, any sense of security you may have is probably
>misguided (IMNSHO).  There *are* people out there who can extract the code.

        A schoolboy with a plugpak and a couple of diodes can
        defeat the code protection on a 'C84.

        A skilled engineer with $100k+ of specialized equipment
        can defeat the code protection on a 'C61.

        This difference in degree is, to me, significant.

        The various responses to this issue boil down to: "no code
        protection scheme is perfect, so the particular protection
        scheme used doesn't matter".

        Taken to its conclusion this argument would suggest we
        shouldn't bother using code protection at all.

        Nevertheless, microcontroller manufacturers continue
        to design chips with code protection facilities, and they
        use the relative merits of their code protection schemes
        to extract competitive advantage in the marketplace.

        We nearly all release chips with code protection enabled.

        We do this to maximise the resources that a competitor
        must expend to reverse engineer our products.

        We do this because it is prudent, and because we usually
        have a legal obligation to do so.

        Where a chip contains information that is the intellectual
        property of the company for which we work and which is
        'company confidential' then we have a duty of non-disclosure.
        This requires us to talk all "reasonable" steps to prevent
        that information being made available to a third party.

        To the best of my knowledge, the code protection of a 'C84
        is weaker than the code protection of a 'C61.  All other
        things being equal, I am obliged to use a 'C61.

        To the best of my knowledge, the code protection of an 'F84
        is the same as the code protection of a 'C84.

        I would like Microchip to improve my knowledge of the
        _relative_ strengths of the code protection schemes
        of these various chips so that I can make informed and
        responsible decisions about my use of them.

        Note that I am _not_ asking Microchip to discuss with me
        the details of their code protection mechanisms.  Indeed,
        these details are 'company confidential' for Microchip!

        What confuses me is that Microchip is prepared to discuss
        the merits of the code protection of its devices (and par-
        ticularly the steps they take to improve code protection),
        excepting the 'C84.

___Bob