Re: ISP programming and code prrotection

From: Ulf Samuelsson (ulf_at_NOSPAMatmel.com)
Date: 03/11/05 

Date: Fri, 11 Mar 2005 19:04:02 +0100

> Depends on the micro. Often, ISP is locked out once you enable the
> protection bits. Sometimes the verification process works by sending
> the new data to the micro twice; first time to burn, second time to
> verify. Sometimes you simply can't verify after setting the protection
> bits, in which case the procedure is to erase the device, program code
> memory, verify code memory, then program security bits.
>
> By definition, anyone who has the power to ISP-burn your micros has
> enough information to copy them.
>
You can put an AVR in a state where you cannot read out and verify but you
can still erase it.
Protection AND reprogrammability.
You can also have a selfprogramming application where you send down a
3DES encrypted file which is decrupted and programmed into the flash.
There is an application note available on that subject. 

-- 
Best Regards
Ulf at atmel dot com
These comments are intended to be my own opinion and they
may, or may not be shared by my employer, Atmel Sweden.

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