AVR-Chat

However, if you disable the SPI then you have done so permanently if all
that you have is an AVR ISP or ISPII.  You'll need a STK500 and a
soldering iron to get it back.

DLC

> On Tue, 23 Oct 2007 16:32:33 +0200 (CEST)
>  "Manne Tallmarken" <mannet@kth.se> wrote:
>> Is it possible to permanently disable all kinds of
>> read/write operations to the flash?
>>
>> Regards,
>>
>> Manne
>>
>
> I don't believe that you can, PERMANENTLY. If the device
> can be parallel programmed, the fuses can be over-ridden by
> erasing the flash (or something like that). Also, devices
> with SPM operation can write to flash, I believe, if it is
> run from the proper code space no matter what the fuses are
> set to.
>
> That is my understanding of such things.
>
> Jim Wagner
> Oregon Research Electronics, Consulting Division
> Tangent, OR, USA
> ---------------------------------------------------------------
> The Think Different Store
> http://www.thinkdifferentstore.com/
> For All Your Mac Gear
> ---------------------------------------------------------------
>
>
>
> Yahoo! Groups Links
>
>
>
>

Well, the thing is that I don't want it to be possible to get the hex-code in any way. Like, programming it, disabling every way to read the flash
and that's it. So actually, write-access would be aloud if the hex-code is erased in the same time...

Manne

> However, if you disable the SPI then you have done so permanently if all
> that you have is an AVR ISP or ISPII.  You'll need a STK500 and a
> soldering iron to get it back.
>
> DLC
>
>> On Tue, 23 Oct 2007 16:32:33 +0200 (CEST)
>>  "Manne Tallmarken" <mannet@kth.se> wrote:
>>> Is it possible to permanently disable all kinds of
>>> read/write operations to the flash?
>>>
>>> Regards,
>>>
>>> Manne
>>>
>>
>> I don't believe that you can, PERMANENTLY. If the device
>> can be parallel programmed, the fuses can be over-ridden by
>> erasing the flash (or something like that). Also, devices
>> with SPM operation can write to flash, I believe, if it is
>> run from the proper code space no matter what the fuses are
>> set to.
>>
>> That is my understanding of such things.
>>
>> Jim Wagner
>> Oregon Research Electronics, Consulting Division
>> Tangent, OR, USA
>> ---------------------------------------------------------------
>> The Think Different Store
>> http://www.thinkdifferentstore.com/
>> For All Your Mac Gear
>> ---------------------------------------------------------------
>>
>>
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>
>
>

AFAIK the AVR hasn't been broken yet.
Once you disable the program read function, the only way to get it
back is after a chip erase, which makes your existing program
dissapear.

So it's not necessary to make the chip essentially a "one time
programmable" device to do this.

On Tue, 23 Oct 2007 19:53:46 +0200 (CEST)
 "Manne Tallmarken" <mannet@kth.se> wrote:
> Well, the thing is that I don't want it to be possible to
> get the hex-code in any way. Like, programming it,
> disabling every way to read the flash
> and that's it. So actually, write-access would be aloud
> if the hex-code is erased in the same time...
> 
> Manne
> 
> 
> > However, if you disable the SPI then you have done so
> permanently if all
> > that you have is an AVR ISP or ISPII.  You'll need a
> STK500 and a
> > soldering iron to get it back.
> >
> > DLC
> >
> >> On Tue, 23 Oct 2007 16:32:33 +0200 (CEST)
> >>  "Manne Tallmarken" <mannet@kth.se> wrote:
> >>> Is it possible to permanently disable all kinds of
> >>> read/write operations to the flash?
> >>>
> >>> Regards,
> >>>
> >>> Manne
> >>>
> >>
> >> I don't believe that you can, PERMANENTLY. If the
> device
> >> can be parallel programmed, the fuses can be
> over-ridden by
> >> erasing the flash (or something like that). Also,
> devices
> >> with SPM operation can write to flash, I believe, if
> it is
> >> run from the proper code space no matter what the
> fuses are
> >> set to.
> >>
> >> That is my understanding of such things.
> >>
> >> Jim Wagner
> >> Oregon Research Electronics, Consulting Division
> >> Tangent, OR, USA
> >>
>
---------------------------------------------------------------

There are places (former Soviet Union?) that "advertise"
being able to recover "any" code. It costs, but it appears
to be real. I think thay they physcically disolve the epoxy
and read it out the flash with something like a scanning
electron microscope.

In the end, there does not appear to be any absolute way to
protect your code. The big question is simply whether or
not it is worth the money to someone else to crack it.

Jim Wagner
Oregon Research Electronics, Consulting Division
Tangent, OR, USA
---------------------------------------------------------------
The Think Different Store
http://www.thinkdifferentstore.com/
For All Your Mac Gear
---------------------------------------------------------------

Thanks for your answer :-)
Well, this is always possible, though I did not really know that there was people who actually were doing it. So I guess it's rather "safe" to
disable a read-without-erasing-the-chip, then.

Manne

> There are places (former Soviet Union?) that "advertise"
> being able to recover "any" code. It costs, but it appears
> to be real. I think thay they physcically disolve the epoxy
> and read it out the flash with something like a scanning
> electron microscope.
>
> In the end, there does not appear to be any absolute way to
> protect your code. The big question is simply whether or
> not it is worth the money to someone else to crack it.
>
> Jim Wagner
> Oregon Research Electronics, Consulting Division
> Tangent, OR, USA
> ---------------------------------------------------------------
> The Think Different Store
> http://www.thinkdifferentstore.com/
> For All Your Mac Gear
> ---------------------------------------------------------------
>