Ron Anthony wrote:
>
> The chip is 100% re-flashable after code protection only if you get your
> hands on the chip again, or recall every unit from around the world to do in
> house flash updates.  The logistics of that are so overwhelmingly
> prohibitive that it can't be done.

Hmmm.

>
> You are presuming that I can get my hands on the chip again once it's in the
> field.  Let's assume that's possible.  Do you think I am going to receive
> envelopes mailed from around the world with chips inside, erase, reflash and
> code protect, and then mail back out to everyone? <snip more complaints>

> My
> only solution to preserve in-the-field-flash-upgradability and lower-half
> security is to go through the coding hell I'm going through as I write this.


Hi Ron, i've been watching this thread and I dont
like to sound mean, but "fix the solution, not the
problem" to butcher a Japanese expression.

There are a number of solutions, given that:
* you want the customer to upgrade their own product
* you must use a 16F877
* code must be protected

How about adding a 80 cent 12C508 to your board,
which programs your 16F877 with data from an external
port (which you must already have). The user could
download new firmware from you via the net, plug their
PC into the product, the 12c508 de-crypts the firmware
and programs the 16F877 in standard ICSP mode.
Full security, solution fixed. This gives you the same
functionality you are asking for now, at the expense
of adding a tiny cheap PIC.

Now before you say that the boards can't be modded
to add the 12c508, you could put the 12c508 plus
a few parts in a tiny potting box, as part of the
programming lead that goes from the product to the
the PC. Neat and cheap.

I think you are just hung up on bootloading, and I don't
know why. It's never been as good a programming option
as a proper ICSP dump. :o)
-Roman

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