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Re: [avr-chat] How can I individualise specific CPUs?

From: Juergen Harms
Subject: Re: [avr-chat] How can I individualise specific CPUs?
Date: Fri, 18 Sep 2009 16:05:50 +0200
User-agent: Thunderbird (X11/20090822)

Great suggestions, many thanks.

Hardwiring unused I/O pins so far did not come to my mind, the necessary soldering will be delicate but should be possible (TQFP64 packages).

Creating a bootloader has been on my todo list for a long time, so far I managed to do without it. But reading your suggestion, I wonder whether the bootloader idea has not an interesting side-issue which I might exploit:

 - reserve a minimum bootloader (512 words), but do not use a bootloader
   (keep the BOOTRST fuse unprogrammed),

 - store the CPU specific data in the bootloader flash section (playing
   with the lock bits to unprotect and later protect the bootloader
   again) - probably possible with a JTAG ICE and avrdude,

 - but: can a programme running in the application flash section read
   data from the bootstrap flash section? (the manual is explicit on
   writing, I did not find any info on reading) - I am optimistic, I
   interpret the lack of "prohibited" statements as an indication that
   data in that section can be read like any address in flash memory.

I will have to do some reading/playing around to see whether and how this is feasible.


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