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<div class="moz-cite-prefix">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.<br>
<br>
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):<br>
<br>
<tt> .balign 2048</tt><tt><br>
</tt><tt> .rept 6 ; Change between 0, 6, 126, and 2046
for flash0, flash1, flash2, and flash3</tt><tt><br>
</tt><tt> nop</tt><tt><br>
</tt><tt> .endr</tt><tt><br>
</tt><tt>loop:</tt><tt><br>
</tt><tt> nop</tt><tt><br>
</tt><tt> inc r16</tt><tt><br>
</tt><tt> cpse r0, r16</tt><tt><br>
</tt><tt> jmp loop</tt><tt><br>
</tt><br>
<br>
The procedure for each test:<br>
1. Invoke the bootloader, and upload program code<br>
2. The program code runs, and toggles a pin to trigger the energy
measurement<br>
3. When the test is finished, the ATMEGA328 toggles the pin again
to stop the measurement<br>
4. Measurement results are downloaded from the energy measurement
board.<br>
<br>
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.<br>
<br>
Hope this helps,<br>
James<br>
<br>
On 27/07/14 17:32, Alex J Lennon wrote:<br>
</div>
<blockquote cite="mid:53D52982.1010603@dynamicdevices.co.uk"
type="cite">
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<br>
<div class="moz-cite-prefix">On 27/07/2014 17:27, James Pallister
wrote:<br>
</div>
<blockquote cite="mid:53D5288E.4090006@bristol.ac.uk" type="cite">
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<div class="moz-cite-prefix">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.<br>
<br>
</div>
</blockquote>
<br>
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?<br>
<br>
(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>
<br>
BR. Alex<br>
<br>
<blockquote cite="mid:53D5288E.4090006@bristol.ac.uk" type="cite">
<div class="moz-cite-prefix"> On 27/07/14 17:25, Steve Kerrison
wrote:<br>
</div>
<blockquote
cite="mid:CANxPWH78iD_Odt_9f+REHOLnPDOA26oGVBzmsY8sNGZ9b9x1cA@mail.gmail.com"
type="cite">
<p dir="ltr">Is JTAG connected during test runs? Interested to
know how much difference that makes, although it should be
constant thus irrelevant.</p>
<div class="gmail_quote">On 27 Jul 2014 17:13, "James
Pallister" <<a moz-do-not-send="true"
href="mailto:James.Pallister@bristol.ac.uk">James.Pallister@bristol.ac.uk</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Hi All,<br>
<br>
Some preliminary findings on variations in the ATMEGA328
chips.<br>
<br>
I've tested 28 chips. For each chip 9 tests were ran:<br>
<br>
<table border="1" cellpadding="2" cellspacing="2"
width="733" height="58">
<tbody>
<tr>
<td valign="top">flash0<br>
</td>
<td valign="top">Test the area of flash
0x0800-0x0810<br>
</td>
</tr>
<tr>
<td valign="top">flash1<br>
</td>
<td valign="top">Test the area of flash
0x080C-0x081C</td>
</tr>
<tr>
<td valign="top">flash2<br>
</td>
<td valign="top">Test the area of flash
0x08FC-0x090C</td>
</tr>
<tr>
<td valign="top">flash3<br>
</td>
<td valign="top">Test the area of flash
0x0FFC-0x100C</td>
</tr>
<tr>
<td valign="top">ram0<br>
</td>
<td valign="top">Repeatedly access 0x0000 - 0x0020<br>
</td>
</tr>
<tr>
<td valign="top">ram1<br>
</td>
<td valign="top">Repeatedly access 0xF007 - 0xF017<br>
</td>
</tr>
<tr>
<td valign="top">alu<br>
</td>
<td valign="top">Perform combinations of mul,
fmul, inc and dec<br>
</td>
</tr>
<tr>
<td valign="top">nop<br>
</td>
<td valign="top">Lots of nops<br>
</td>
</tr>
<tr>
<td valign="top">branch<br>
</td>
<td valign="top">Repeatedly branch randomly in low
flash<br>
</td>
</tr>
</tbody>
</table>
<br>
Each test was run 8 times, and outliers excluded. All
were run in the same harness, with the same crystal,
resistors, etc.<br>
<br>
Results across each test. These show the distributions
of the measurements taken, where the distribution
consists of the 28 chips.<br>
<img src="cid:part2.05080009.05030804@bristol.ac.uk"
alt=""><br>
<br>
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.<br>
<br>
For each chip:<br>
<img src="cid:part3.01070602.08020604@bristol.ac.uk"
alt=""><br>
Mean power for each chip:<br>
<img src="cid:part4.07050607.09060205@bristol.ac.uk"
alt=""><br>
<br>
<br>
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).<br>
<br>
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.<br>
<img src="cid:part5.06000806.08030506@bristol.ac.uk"
alt=""><br>
Legend for the above graph:<br>
<table border="1" cellpadding="2" cellspacing="2"
width="318" height="58">
<tbody>
<tr>
<td valign="top">Blue cross<br>
</td>
<td valign="top">ram1<br>
</td>
</tr>
<tr>
<td valign="top">Red star<br>
</td>
<td valign="top">ram0<br>
</td>
</tr>
<tr>
<td valign="top">Green plus<br>
</td>
<td valign="top">alu<br>
</td>
</tr>
<tr>
<td valign="top">Black plus<br>
</td>
<td valign="top">flash3<br>
</td>
</tr>
<tr>
<td valign="top">Green cross<br>
</td>
<td valign="top">flash2<br>
</td>
</tr>
<tr>
<td valign="top">Blue star<br>
</td>
<td valign="top">flash1<br>
</td>
</tr>
<tr>
<td valign="top">Red plus<br>
</td>
<td valign="top">flash0<br>
</td>
</tr>
<tr>
<td valign="top">Black star<br>
</td>
<td valign="top">nop<br>
</td>
</tr>
</tbody>
</table>
<br>
<br>
Any thoughts / ideas for more tests are welcome.<br>
<br>
<br>
James<br>
</div>
</blockquote>
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</blockquote>
<br>
<br>
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