[MAGEEC] Chip variations: tests, results, and graphs
James Pallister
James.Pallister at bristol.ac.uk
Sun Jul 27 17:47:58 BST 2014
Ah yes, the flash tests were purely for read access from different areas
of flash, based on the idea that there may be silicon variation between
parts of the address space.
It was actually program execution from different areas of flash, by
putting a tight loop in a specific area and measuring the power. For
example (flash1):
.balign 2048
.rept 6 ; Change between 0, 6, 126, and 2046 for flash0,
flash1, flash2, and flash3
nop
.endr
loop:
nop
inc r16
cpse r0, r16
jmp loop
The procedure for each test:
1. Invoke the bootloader, and upload program code
2. The program code runs, and toggles a pin to trigger the energy
measurement
3. When the test is finished, the ATMEGA328 toggles the pin again to
stop the measurement
4. Measurement results are downloaded from the energy measurement board.
I haven't done any flash writing/erasing tests, but I agree it would be
interesting to do some. I'd expect the power during a write/erase to be
much higher.
Hope this helps,
James
On 27/07/14 17:32, Alex J Lennon wrote:
>
> On 27/07/2014 17:27, James Pallister wrote:
>> No JTAG - the chips are flashed with a bootloader, which is only
>> active on chip reset. Everything is programmed via a USB-to-serial
>> thingy.
>>
>
> Sorry, I don't think I'm understanding fully James. So the flash area
> tests are via JTAG? I guess that would mean that the test is a read
> only test?
>
> (I'm just asking because I'm quite interested in power utilisation
> during write/erase cycles vs read. If you're not doing that could I
> suggest it might be an interesting test?)
>
> BR. Alex
>
>> On 27/07/14 17:25, Steve Kerrison wrote:
>>>
>>> Is JTAG connected during test runs? Interested to know how much
>>> difference that makes, although it should be constant thus irrelevant.
>>>
>>> On 27 Jul 2014 17:13, "James Pallister"
>>> <James.Pallister at bristol.ac.uk
>>> <mailto:James.Pallister at bristol.ac.uk>> wrote:
>>>
>>> Hi All,
>>>
>>> Some preliminary findings on variations in the ATMEGA328 chips.
>>>
>>> I've tested 28 chips. For each chip 9 tests were ran:
>>>
>>> flash0
>>> Test the area of flash 0x0800-0x0810
>>> flash1
>>> Test the area of flash 0x080C-0x081C
>>> flash2
>>> Test the area of flash 0x08FC-0x090C
>>> flash3
>>> Test the area of flash 0x0FFC-0x100C
>>> ram0
>>> Repeatedly access 0x0000 - 0x0020
>>> ram1
>>> Repeatedly access 0xF007 - 0xF017
>>> alu
>>> Perform combinations of mul, fmul, inc and dec
>>> nop
>>> Lots of nops
>>> branch
>>> Repeatedly branch randomly in low flash
>>>
>>>
>>> Each test was run 8 times, and outliers excluded. All were run
>>> in the same harness, with the same crystal, resistors, etc.
>>>
>>> Results across each test. These show the distributions of the
>>> measurements taken, where the distribution consists of the 28 chips.
>>>
>>>
>>> From the first graph: there is a significant different, even on
>>> a day to day basis. I'm not sure what causes this - I'd expect
>>> the power to be lower at lower temperatures, which we don't see.
>>>
>>> For each chip:
>>>
>>> Mean power for each chip:
>>>
>>>
>>>
>>> The average power changes quite a lot, going from < 80mW to >
>>> 100mW. In almost all cases, the average power was higher on
>>> Saturday - not sure why this is, the temperature difference was
>>> only 3-4 degrees (and I'd expect the temperature to go down with
>>> lower temperature).
>>>
>>> The chips tend to vary as a whole, e.g. rather than the ALU
>>> varying significantly in one part rather than another. The
>>> following graph marks the average power for each test, divided
>>> by test type (different color/marker combinations) per chip.
>>> This should allow hopefully allow us to do a calibration run first.
>>>
>>> Legend for the above graph:
>>> Blue cross
>>> ram1
>>> Red star
>>> ram0
>>> Green plus
>>> alu
>>> Black plus
>>> flash3
>>> Green cross
>>> flash2
>>> Blue star
>>> flash1
>>> Red plus
>>> flash0
>>> Black star
>>> nop
>>>
>>>
>>>
>>> Any thoughts / ideas for more tests are welcome.
>>>
>>>
>>> James
>>>
>>
>>
>>
>> _______________________________________________
>> mageec mailing list
>> mageec at mageec.org
>> http://mageec.org/cgi-bin/mailman/listinfo/mageec
>
> --
>
> Dynamic Devices Ltd <http://www.dynamicdevices.co.uk/>
>
> Alex J Lennon / Director
> 1 Queensway, Liverpool L22 4RA
>
> mobile: +44 (0)7956 668178
>
> Linkedin <http://www.linkedin.com/in/alexjlennon> Skype
> <skype:alexjlennon?add>
>
> This e-mail message may contain confidential or legally privileged
> information and is intended only for the use of the intended
> recipient(s). Any unauthorized disclosure, dissemination,
> distribution, copying or the taking of any action in reliance on the
> information herein is prohibited. E-mails are not secure and cannot be
> guaranteed to be error free as they can be intercepted, amended, or
> contain viruses. Anyone who communicates with us by e-mail is deemed
> to have accepted these risks. Company Name is not responsible for
> errors or omissions in this message and denies any responsibility for
> any damage arising from the use of e-mail. Any opinion and other
> statement contained in this message and any attachment are solely
> those of the author and do not necessarily represent those of the company.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 120718 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0007.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 176160 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0008.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 44187 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0009.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 79329 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0010.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 3997 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0011.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 631 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0012.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 800 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/95845a61/attachment-0013.png>
More information about the mageec
mailing list