Now, let me put forth, contrary to Michael Karas, I don't think we need to discuss the case when the micro is left unlocked at all - nobody is THAT naive.

Whether copying is legal, makes sense or not - all this is irrelevant once it happens. And it DOES happen. Fullstop.

The only question is the cost of copying. It might come as a surprise for some, but the general purpose micros which are around for some time can be unlocked in a snap, and the cost might be as low as a few hundred $s (I was once told, that a typical pricelist for such "services" starts at $99 for notoriously known bad protection devices such as some of the the PIC16's).

This price can be slightly increased by using a rarely used microcontroller, using a combination of features in the whole product which increase the cost of copying. Although it sounds desperate, in some cases physical destruction (including zapping) of pins needed for programming might make sense, although it undoubtedly might influence reliability - nevertheless, this might not matter (e.g. in toys or other devices with short expected lifetime and easy replacement). One of other desperate attempts is potting the microcontroller or the whole product. Other schemes involve batteries and volatile RAMs. Yet another schemes involve EPROM (OTP) or ROM based products.

Now one needs to calculate with this price, when making a product. Sometimes it is easy to avoid troubles with copying at all (e.g. providing a product to a single trusted customer), but in some "business models" it cannot be simply avoided. The developer simply MUST be aware of the problem.

The trouble is, that no manufacturer admits a low price of copying publicly - but on the other hand, many of them (Atmel including) make devices much better protected, but for a dedicated market (namely smartcards is one of the best known).

So, I think, there is no need to tabooize the problem nor to neglect it. I think this is the right forum to talk about it...

Jan Waclawek

PS. Unlocking pre-1998 AT89C2051 is a piece of cake, I'd not give even $99 for it... :-)